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Silent Witness Title card ( 2015 -- 2017 ) Genre Crime drama Created by Nigel McCrery Starring Amanda Burton William Gaminara Tom Ward Emilia Fox David Caves Liz Carr Richard Lintern Theme music composer John Harle Composer ( s ) Sheridan Tongue Country of origin United Kingdom Original language ( s ) English No. of series 21 No. of episodes 184 ( list of episodes ) Production Executive producer ( s ) Phillipa Giles Laura Mackie Jessica Pope Producer ( s ) Sharon Bloom Anne Pivcevic Ceri Meyrick Running time 45 minutes ( Series 1 -- 5 ) 60 minutes ( Series 6 -- present ) Distributor BBC Studios Release Original network BBC One Audio format Stereo Original release 21 February 1996 ( 1996 - 02 - 21 ) -- present External links Website Silent Witness is a British television crime drama series , produced by the BBC , which focuses on a team of forensic pathology experts and their investigations into various crimes . First broadcast in 1996 , the series was created by Nigel McCrery , a former murder squad detective based in Nottingham . ( He later went on to create the series New Tricks , with writer Roy Mitchell . ) Twenty - one series of Silent Witness have been broadcast since 1996 . Amanda Burton starred as primary character Dr. Sam Ryan before leaving the show during the eighth series . Since her departure the series has featured an ensemble cast , currently consisting of Emilia Fox , David Caves , Liz Carr and Richard Lintern . The programme is broadcast in more than 235 territories , including ABC in Australia , Showcase and the Knowledge Network in Canada , KRO in the Netherlands , TV One and Prime in New Zealand , and BBC America in the United States . Silent Witness continues to achieve good audience ratings in the UK . In 2011 , for example , Series 14 attracted an average audience of nine million viewers . Contents ( hide ) 1 Background 2 Episodes 3 Characters 3.1 Main 3.2 Main characters 3.3 Other characters 3.4 Police 4 Novels 5 See also 6 References 7 External links Background ( edit ) The main character in the original series was based on Professor Helen Whitwell , a forensic pathologist based in Sheffield , whom McCrery had known while serving as a police officer . The programme followed the activities of pathologist Sam Ryan , played by Amanda Burton , until she departed early in the eighth series . There was a succession of regular supporting characters , changing almost every series , but Dr Leo Dalton ( William Gaminara ) and Dr Harry Cunningham ( Tom Ward ) , who were introduced in the sixth series , continued as lead characters following Ryan 's departure , with Dalton replacing her as professor . A new character , Dr Nikki Alexander ( Emilia Fox ) , was introduced in the eighth series . While working as a forensic anthropologist , she appropriates facilities and software in the pathology department to analyse an Iron Age find , with the belated , bemused and begrudging approval of Dalton . Dr Alexander is able to assist in a set of cases being investigated by the team , as it turns out she has `` worked in forensic pathology in Johannesburg for six months '' and is certified by the Home Office to practise . She eventually overcomes Leo 's reluctance and , with Harry 's support , is offered and accepts a position on the team . During the fifteenth series Dr Cunningham leaves to accept a position in New York City . He is replaced by forensics expert Jack Hodgson ( David Caves ) and his assistant Clarissa Mullery ( Liz Carr ) . During the sixteenth series Dr Dalton is killed in an explosion . His replacement , Dr Thomas Chamberlain ( Richard Lintern ) , is introduced at the start of the seventeenth series . Although the show focuses heavily on areas of pathology , the police also have a presence in each case . During later series of the show detectives and investigators tend to differ from episode to episode , with guest artists appearing in these roles . However , during the early years of the show several characters appeared regularly to investigate each case . The first three series were set in Cambridge . This changed to London from the start of the fourth series , following Sam as she took up an academic position . Each series is typically made up of a series of two - part stories . The first nine series typically featured eight episodes ( four two - part stories ) , increased to ten episodes ( five two - part stories ) from the tenth series onwards . In 1998 the writer John Milne received an Edgar Award from the Mystery Writers of America for the second series episode `` Blood , Sweat and Tears '' . In the United States the series airs during ' Mystery Monday ' on BBC America . The series airs in Norway under the title `` Tause vitner '' on the Norwegian Broadcasting Corporation NRK and in Sweden on TV4 under the name `` Tyst vittne '' . Both the Norwegian and Swedish titles are direct translations . The show is also broadcast in the Netherlands by public broadcaster KRO , Belgium on VRT channel Canvas and in Finland on the Finnish Broadcasting Company Yle using the name `` Hiljainen todistaja '' , which is also a direct translation of the original title . The theme music featured in the series is entitled Silencium and is performed by John Harle . The arrangement , for chamber orchestra and soprano saxophone solo , was first performed as part of the Canterbury Festival on 22 October 2011 . The vocal section is performed by Sarah Leonard . The incidental music used in the series is written by the BAFTA - nominated composer Sheridan Tongue . In August 2012 the series came under criticism for being `` unduly gruesome '' . Controversy was specifically focused on the fifteenth - series episode Redhill , written by Ed Whitmore . The BBC responded with the following : `` As programme makers we take our responsibility to the audience extremely seriously and try to make sure we strike the right balance between compelling drama without being unnecessarily graphic . Towards the end of the first episode , we had established that DI Bridges and Officer Kessler had previously worked together and that he was the one very much in control . The final scene was not an attempt to gratuitously shock the audience ; it was rooted in character and research , showing just what DI Bridges was prepared to do for her colleague for the sake of her family , as well as the brutality that Kessler was capable of . We acknowledge that certain scenes may have been challenging , but we filmed and presented them in such a way as to make sure that although as a viewer the implication was there , it was never actually shown . Silent Witness is now in its fifteenth series , and we believe the general tone and content is widely recognised by its regular audience . It 's fair to say the show is known for tackling challenging stories and exploring adult themes and we do n't feel the content of these episodes would have gone beyond viewers ' expectations . As well as scheduling the series after the watershed , we made sure the content was widely publicised and gave a warning before both episodes . '' Episodes ( edit ) Further information : List of Silent Witness episodes Characters ( edit ) Main ( edit ) Actor Character Series 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Amanda Burton Professor Sam Ryan Main Absent William Gaminara Professor Leo Dalton Absent Main Absent Guest Absent Tom Ward Dr. Harry Cunningham Absent Main Absent Emilia Fox Dr. Nikki Alexander Absent Main David Caves Jack Hodgson Absent Main Liz Carr Clarissa Mullery Absent Main Richard Lintern Dr. Thomas Chamberlain Absent Main Main characters ( edit ) Professor Sam Ryan ( Amanda Burton ) -- Series 1 -- 8 . Sam originally lived and worked in Cambridge , but moved to London at the end of series three after she was offered the job of professor at a university . Sam departed in the first episode of series eight , `` A Time To Heal '' . Sam returned home to Ireland after a member of her family was implicated in a murder . Professor Leo Dalton ( William Gaminara ) -- Series 6 -- 16 . Leo first appeared in the episode `` The Fall Out '' , where he was nothing more than a simple doctor . However , he was promoted to professor after former professor Sam Ryan left . In the episode `` Ghosts '' , both his wife , Theresa , and his daughter , Cassie , are killed in a car accident . He began a relationship with fellow professor Janet Mander in `` Death 's Door '' , but ended their relationship in the episode `` Domestic '' . Leo often took a strong opinion on cases and became emotionally involved . He died in the series 16 finale `` Greater Love '' , when he sacrificed himself to save many others from a terrorist bomb explosion . He briefly appeared in a flashback in the last episode of series 20 . Dr. Harry Cunningham ( Tom Ward ) -- Series 6 -- 15 . Harry started out life as a junior doctor , who worked as an apprentice alongside Sam and Leo . However , he soon qualified as a pathologist , and has worked on equal footing with the team for a number of years . Harry was single , and lived alone , but has had several romantic relationships , including an ongoing ' will they - wo n't they ' relationship with his colleague Nikki . Harry left the team to accept a professorship in New York at the end of series 15 . As this was decided after filming was completed , and the stories were reordered , with `` And Then I Fell in Love '' airing last , where it was originally scheduled as the second episode , his departure was never on screen . Dr. Nikki Alexander ( Emilia Fox ) -- since Series 8 . Originally appearing in the episode `` Nowhere Fast '' , Nikki was originally assigned to the Lyell Centre to defuse the tension between Harry and Leo after Sam 's departure . However , Nikki soon became a permanent fixture within the team , and although she features more prominently in the series , holds a lower rank in pathology than Leo . Despite her native home being South Africa , Nikki regards the United Kingdom as her second home , as the reason for her departure from the country lies solely in the hands of her father , Victor , as explained in the episode `` Double Dare '' . Nikki often flirted with colleague Harry , and even invited him to stay at her house after his flat blew up in an explosion . Nikki and Harry were in an ongoing ' will they - wo n't they ' relationship until he left in Series 15 . As well as this , she developed a close relationship with Leo and looked up to him as a father figure . Jack Hodgson ( David Caves ) -- since Series 16 . Before his arrival at the Lyell Centre , Jack was a forensic scientist for the police , working on regular murder investigations . However , when he is called out to the scene of a man 's suspicious death in `` Change '' , both Nikki and Leo spot his potential , and looking for a senior colleague to replace Harry , decide to offer Jack a job as the centre 's forensic expert . Jack is close friends with colleague Clarissa Mullery , whom he invites to work with him at the Lyell Centre , much to Leo 's surprise . In his spare time , Jack is a cage fighter , and splits his home life between forensic research and training for his next fight . Clarissa Mullery ( Liz Carr ) -- since Series 16 . Clarissa is Jack 's personal lab assistant , who first appears in the episode `` Change '' , when Jack invites her to work at the Lyell Centre with him , much to Leo 's surprise . She is a disabled by an unspecified condition and uses an electric wheelchair . She has a very cheeky side , first making a quip at Leo after he fails to recognise who she is on her first arrival . Clarissa had clearly worked for Jack for a long period before his appointment at the Lyell Centre ; however , the exact period of time is unknown . Dr. Thomas Chamberlain ( Richard Lintern ) -- since Series 17 . Thomas Chamberlain has taken over as head of the Lyell Centre from Leo who died at the end of series 16 . He is an experienced forensic pathologist with a renowned reputation in toxicology and is described as charming , charismatic and socially shrewd . His first encounters with Jack , Nikki and Clarissa did not go well but they were gradually warmed to him . It is revealed in the last episode of his first series that his wife has left him just before he started working at the Lyell Centre , and has taken their daughter with her . Other characters ( edit ) Dr. Trevor Stewart ( William Armstrong ) -- Series 1 -- 3 . As well as being a pathologist in his own right , Trevor was Sam 's business partner , owning half of the morgue and its facilities . Trevor decided to stay in Cambridge with his friends and family when Sam accepted the professorship position at a university in London and moved away at the end of series three . Dr. Fred Dale ( Sam Parks ) -- Series 1 -- 3 . Fred was Sam 's main assistant during post mortems and on visits to crime scenes , often identifying DNA samples at the scene of the crime , and linking them to those responsible . He was also notable for not having many speaking lines , and regularly appearing without speaking . His fate at the end of series three was not revealed . Professor Janet Mander ( Jaye Griffiths ) -- Series 12 -- 15 . Janet is a psychological profiler who assists the police in cases of serial offences . She began a relationship with Leo in the episode `` Safe '' , and they lived together as partners until Leo ended the relationship in `` Redhill '' . She recurringly worked alongside the team to provide them with information in order to get an idea of the suspect they are looking for . Janet decided to move away from London after Leo ended their relationship . Dr. Charlie Gibbs ( Wunmi Mosaku ) -- Series 13 . A junior doctor and lab technician , who was appointed to work with the team by Professor Dalton . Dr. Zak Khan ( Arsher Ali ) -- Series 14 . A junior doctor who worked his forensic science apprenticeship with the team , to learn the ropes of the profession . Wyn Ryan ( Ruth McCabe ) -- Series 1 -- 3 . Professor Ryan 's sister , who , after coming over to visit her from her home in Ireland , ended up living with her on a permanent basis . Ricky Ryan ( Matthew Steer ) -- Series 1 . Wyn 's son and Sam 's nephew , who regularly got into trouble and was expelled from school for very poor behaviour . Rosemary Mason ( Jane Hazlegrove ) -- Series 6 -- 7 . The main receptionist at the Lyell Centre , before the change in focus from university department to purely commercial pathology . Police ( edit ) Superintendent Helen Farmer ( Clare Higgins ) -- Series 1 . A superintendent , and Tom Adams ' boss and mentor , who accompanied him on investigating several cases during his time in the force . Detective Chief Inspector Tom Adams ( John McGlynn ) -- Series 1 . An investigator with the Cambridgeshire police force , who had an affair with Kerry Cox , before her death . Detective Constable Kerry Cox ( Ruth Gemmell ) -- Series 1 . A junior trainee detective who had an affair with Tom Adams , but was later killed in a freak accident in a hospital basement . Detective Constable Marcia Evans ( Janice Acquah ) -- Series 1 . A fellow junior trainee detective for the Cambridgeshire police force , who resigned after Kerry Cox 's death . Superintendent Peter Ross ( Mick Ford ) -- Series 2 . A superintendent , and an ex-boyfriend of Sam 's , who believed in a strong relationship between the police and the pathology lab . Detective Chief Inspector Rachel Selway ( Nicola Redmond ) -- Series 2 . Tom Adams ' replacement , following his resignation from the force . She joined the team alongside junior sergeant Tony Speed . Detective Sergeant Tony Speed ( Richard Huw ) -- Series 2 . A junior sergeant , who joined the team alongside his superior officer , Rachel Selway . He knew Peter Ross from a previous posting . Detective Chief Inspector Michael Connor ( Nick Reding ) -- Series 3 -- 4 . A detective chief inspector , and old friend of Sam 's , whom she met during her junior years at university . Detective Sergeant Rob Bradley ( Mark Letheren ) -- Series 3 . A detective sergeant , who as Connor 's junior officer , accompanied him with the investigating in the cases which he was assigned to . Novels ( edit ) During the early years of the show , series creator McCrery wrote and published a number of tie - in novels relating to the series , following Sam Ryan ( Amanda Burton ) and Trevor Stewart ( William Armstrong ) , as well as former main character Superintendent Tom Adams ( John McGlynn ) , and brand new character DS Stanley Sharman , with Burton generally appearing on the front cover of each novel . The fifth novel , due to be published in 2003 , was placed on indefinite hold , and has never been released . Title No . Publication Date `` A Case for the Defence '' 9 September 1996 Walking home from a night out , Sam stumbles upon the remains of a mutilated body on a footpath in the Northwick graveyard . Evidence suggests that the killing may be linked to a particularly ritualistic form of the black arts , but Sam is unconvinced as the murder bears an uncanny resemblance to another murder committed in the same town many years ago . When a second body is discovered , Sam 's evidence is called into question , and is used to create the information that the police need to solve the case , before the killer strikes again . As Sam and Trevor uncover information surrounding the circumstances of the murders , elements that once seemed like coincidences soon appear to belong to a more horrific plan . `` Strange Screams of Death '' 3 August 1998 Sam is tasked with investigating the circumstances surrounding the death of a woman whose body is discovered in a disused shed at a former American airbase on the outskirts of Cambridge . The post mortem reveals that she had been violently raped , before being tortured , and viciously murdered . When a second body is discovered in similar circumstances , Sam finds herself dealing with a serial killer , who has the hunger to slaughter again . Can her profile of information find the identity of the killer before it is too late ? Meanwhile , as Tom Adams closes in on his prime suspect , Sam discovers that he may not be working alone , and a search is launched to find the accomplice of a dangerous criminal . `` The Spider 's Web '' 2 August 1999 Sam is asked to perform a second autopsy on a teenage boy who was killed in a tragic joyriding accident , when despite his parents ' protests , the results of the autopsy seem clear -- he died of multiple injuries consistent with a high - speed car crash . However , as Trevor performed the post mortem , Sam is reluctant to go up against her friend and colleague , in an attempt to find the answers that the family are looking for . However , reading Trevor 's post mortem report prompts Sam to go ahead with the second autopsy , and her findings seem to suggest that the accident may have been no such thing . But neither Trevor nor Superintendent Tom Adams accepts her findings , and believe that she is reading between the lines . `` Faceless Strangers '' 3 September 2001 When the wife and beau of a local member of parliament is found dead in her own home , Superintendent Tom Adams calls upon Sam and the entire resources of the Cambridge Constabulary , in an attempt to further his career , and solve the case as quickly as possible . However , his investigation is halted by the discovery of the decomposed body of a homeless drug addict in the local underground toilet block . When Adams dismisses the death as an open and shut case , one of his juniors , DS Stanley Sharman , decides to enlist Sam 's help , to discover the identity of the dead woman -- and discover just who is responsible for her death . Meanwhile , Adams is determined to crack his case . `` In Search of Evil '' 5 3 November 2003 When the body of elderly widow Violet Thorpe is discovered beneath the floor of her own cellar , Sam quickly establishes that she had been poisoned , and died more than a year prior to the discovery of her body . Meanwhile , the victim 's contact with an old friend living in Brighton , appears to be a vital piece of evdidence in discovering who is responsible for her murder . When Sam and DS Stanley Sharman visit the address of the old friend in Brighton , they find themselves on a bizarre trail of a mentally deranged killer , who appears to be travelling up and down the country in search of lonely old ladies to kill , and Sam finds herself in a race to discover the identity of one of the country 's most prolific serial killers . See also ( edit ) The use of forensic pathology in the investigation of crime has been the central theme of several TV mystery - suspense dramas , including : Wojeck , Canada ( CBC ) , 1966 Quincy , M.E. , US ( NBC ) , 1976 Da Vinci 's Inquest , Canada ( CBC ) , 1998 Waking the Dead , UK ( BBC ) , 2000 CSI : Crime Scene Investigation , US ( CBS ) , 2000 Crossing Jordan , US ( NBC ) , 2001 CSI : Miami , US ( CBS ) , 2002 CSI : NY , US ( CBS ) , 2004 Bones , US ( Fox ) , 2005 RIS Delitti Imperfetti , Italy ( Canale 5 ) , 2005 R.I.S , police scientifique , France ( TF1 ) , 2006 Post Mortem , Germany ( RTL ) , 2007 Rizzoli & Isles , US ( TNT ) , 2010 Body of Proof , US ( ABC ) , 2011 References ( edit ) Jump up ^ Silent Witness entry at TV.com Jump up ^ `` BBC - Silent Witness - Media Centre '' . Jump up ^ `` Silent Witness '' . ABC Television . Jump up ^ tvnz.co.nz/silent-witness/show-432523 Jump up ^ `` Drama '' . Jump up ^ Liz Jaques . `` TV Overnight Ratings ; Retrieved 25 January 2011 '' . MediaTel . Retrieved 2014 - 07 - 21 . Jump up ^ `` NRK TV -- Tause vitner '' . NRK TV . Jump up ^ `` Tyst vittne -- tv4.se '' . Jump up ^ `` Silent Witness release info '' . IMDb . IMDb . Retrieved 18 May 2015 . Jump up ^ `` John Harle '' . musicsalesclassical.com . Retrieved 3 February 2015 . Jump up ^ `` John Harle -- Discography '' . johnharle.com . Retrieved 3 February 2015 . Jump up ^ `` The Fall and Silent Witness criticised for ' voyeuristic ' misogyny by writer Lucinda Coxon '' . 23 August 2016 . Jump up ^ `` Complaints -- Silent Witness , upsetting scenes , BBC One 22 and 23 April 2012 '' . BBC . Retrieved 2014 - 07 - 21 . Jump up ^ `` Arsher Ali '' . Retrieved 9 September 2011 . Jump up ^ `` In Search of Evil ( Silent Witness ) : Amazon.co.uk : Mccrery Nigel : Books '' . Amazon.co.uk . Retrieved 2014 - 07 - 21 . External links ( edit ) Silent Witness at BBC Programmes Silent Witness on IMDb Silent Witness at TV.com Silent Witness at epguides.com Retrieved from `` https://en.wikipedia.org/w/index.php?title=Silent_Witness&oldid=834305269 '' Categories : 1996 British television programme debuts 1990s British crime drama television series 1990s British mystery television series 2000s British crime drama television series 2000s British mystery television series 2010s British crime drama television series 2010s British mystery television series BBC crime television programmes BBC high definition programmes BBC television dramas Edgar Award - winning works English - language television programs Television shows about death Television shows set in the United Kingdom Hidden categories : Use dmy dates from January 2014 Use British English from January 2014 Pages using deprecated image syntax Talk Contents About Wikipedia Wikiquote Deutsch Español فارسی Français 한국어 Italiano עברית Nederlands Norsk Polski Русский Slovenčina Suomi Svenska 5 more Edit links This page was last edited on 5 April 2018 , at 00 : 26 . Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply . By using this site , you agree to the Terms of Use and Privacy Policy . Wikipedia ® is a registered trademark of the Wikimedia Foundation , Inc. , a non-profit organization . About Wikipedia 
how did leo dalton die in silent witness
Silent Witness Title card ( 2015 -- 2017 ) Genre Crime drama Created by Nigel McCrery Starring Amanda Burton William Gaminara Tom Ward Emilia Fox David Caves Liz Carr Richard Lintern Theme music composer John Harle Composer ( s ) Sheridan Tongue Country of origin United Kingdom Original language ( s ) English No. of series 21 No. of episodes 184 ( list of episodes ) Production Executive producer ( s ) Phillipa Giles Laura Mackie Jessica Pope Producer ( s ) Sharon Bloom Anne Pivcevic Ceri Meyrick Running time 45 minutes ( Series 1 -- 5 ) 60 minutes ( Series 6 -- present ) Distributor BBC Studios Release Original network BBC One Audio format Stereo Original release 21 February 1996 ( 1996 - 02 - 21 ) -- present External links Website Silent Witness Title card ( 2015 -- 2017 ) Genre Crime drama Created by Nigel McCrery Starring Amanda Burton William Gaminara Tom Ward Emilia Fox David Caves Liz Carr Richard Lintern Theme music composer John Harle Composer ( s ) Sheridan Tongue Country of origin United Kingdom Original language ( s ) English No. of series 21 No. of episodes 184 ( list of episodes ) Production Executive producer ( s ) Phillipa Giles Laura Mackie Jessica Pope Producer ( s ) Sharon Bloom Anne Pivcevic Ceri Meyrick Running time 45 minutes ( Series 1 -- 5 ) 60 minutes ( Series 6 -- present ) Distributor BBC Studios Release Original network BBC One Audio format Stereo Original release 21 February 1996 ( 1996 - 02 - 21 ) -- present External links Website Silent Witness is a British television crime drama series , produced by the BBC , which focuses on a team of forensic pathology experts and their investigations into various crimes . First broadcast in 1996 , the series was created by Nigel McCrery , a former murder squad detective based in Nottingham . ( He later went on to create the series New Tricks , with writer Roy Mitchell . ) Twenty - one series of Silent Witness have been broadcast since 1996 . Amanda Burton starred as primary character Dr. Sam Ryan before leaving the show during the eighth series . Since her departure the series has featured an ensemble cast , currently consisting of Emilia Fox , David Caves , Liz Carr and Richard Lintern . The programme is broadcast in more than 235 territories , including ABC in Australia , Showcase and the Knowledge Network in Canada , KRO in the Netherlands , TV One and Prime in New Zealand , and BBC America in the United States . Silent Witness continues to achieve good audience ratings in the UK . In 2011 , for example , Series 14 attracted an average audience of nine million viewers . The main character in the original series was based on Professor Helen Whitwell , a forensic pathologist based in Sheffield , whom McCrery had known while serving as a police officer . The programme followed the activities of pathologist Sam Ryan , played by Amanda Burton , until she departed early in the eighth series . There was a succession of regular supporting characters , changing almost every series , but Dr Leo Dalton ( William Gaminara ) and Dr Harry Cunningham ( Tom Ward ) , who were introduced in the sixth series , continued as lead characters following Ryan 's departure , with Dalton replacing her as professor . A new character , Dr Nikki Alexander ( Emilia Fox ) , was introduced in the eighth series . While working as a forensic anthropologist , she appropriates facilities and software in the pathology department to analyse an Iron Age find , with the belated , bemused and begrudging approval of Dalton . Dr Alexander is able to assist in a set of cases being investigated by the team , as it turns out she has `` worked in forensic pathology in Johannesburg for six months '' and is certified by the Home Office to practise . She eventually overcomes Leo 's reluctance and , with Harry 's support , is offered and accepts a position on the team . During the fifteenth series Dr Cunningham leaves to accept a position in New York City . He is replaced by forensics expert Jack Hodgson ( David Caves ) and his assistant Clarissa Mullery ( Liz Carr ) . During the sixteenth series Dr Dalton is killed in an explosion . His replacement , Dr Thomas Chamberlain ( Richard Lintern ) , is introduced at the start of the seventeenth series . Although the show focuses heavily on areas of pathology , the police also have a presence in each case . During later series of the show detectives and investigators tend to differ from episode to episode , with guest artists appearing in these roles . However , during the early years of the show several characters appeared regularly to investigate each case . The first three series were set in Cambridge . This changed to London from the start of the fourth series , following Sam as she took up an academic position . Each series is typically made up of a series of two - part stories . The first nine series typically featured eight episodes ( four two - part stories ) , increased to ten episodes ( five two - part stories ) from the tenth series onwards . In 1998 the writer John Milne received an Edgar Award from the Mystery Writers of America for the second series episode `` Blood , Sweat and Tears '' . In the United States the series airs during ' Mystery Monday ' on BBC America . The series airs in Norway under the title `` Tause vitner '' on the Norwegian Broadcasting Corporation NRK and in Sweden on TV4 under the name `` Tyst vittne '' . Both the Norwegian and Swedish titles are direct translations . The show is also broadcast in the Netherlands by public broadcaster KRO , Belgium on VRT channel Canvas and in Finland on the Finnish Broadcasting Company Yle using the name `` Hiljainen todistaja '' , which is also a direct translation of the original title . The theme music featured in the series is entitled Silencium and is performed by John Harle . The arrangement , for chamber orchestra and soprano saxophone solo , was first performed as part of the Canterbury Festival on 22 October 2011 . The vocal section is performed by Sarah Leonard . The incidental music used in the series is written by the BAFTA - nominated composer Sheridan Tongue . In August 2012 the series came under criticism for being `` unduly gruesome '' . Controversy was specifically focused on the fifteenth - series episode Redhill , written by Ed Whitmore . The BBC responded with the following : `` As programme makers we take our responsibility to the audience extremely seriously and try to make sure we strike the right balance between compelling drama without being unnecessarily graphic . Towards the end of the first episode , we had established that DI Bridges and Officer Kessler had previously worked together and that he was the one very much in control . The final scene was not an attempt to gratuitously shock the audience ; it was rooted in character and research , showing just what DI Bridges was prepared to do for her colleague for the sake of her family , as well as the brutality that Kessler was capable of . We acknowledge that certain scenes may have been challenging , but we filmed and presented them in such a way as to make sure that although as a viewer the implication was there , it was never actually shown . Silent Witness is now in its fifteenth series , and we believe the general tone and content is widely recognised by its regular audience . It 's fair to say the show is known for tackling challenging stories and exploring adult themes and we do n't feel the content of these episodes would have gone beyond viewers ' expectations . As well as scheduling the series after the watershed , we made sure the content was widely publicised and gave a warning before both episodes . '' Actor Character Series 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Amanda Burton Professor Sam Ryan Main Absent William Gaminara Professor Leo Dalton Absent Main Absent Guest Absent Tom Ward Dr. Harry Cunningham Absent Main Absent Emilia Fox Dr. Nikki Alexander Absent Main David Caves Jack Hodgson Absent Main Liz Carr Clarissa Mullery Absent Main Richard Lintern Dr. Thomas Chamberlain Absent Main Actor Character Series 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Amanda Burton Professor Sam Ryan Main Absent William Gaminara Professor Leo Dalton Absent Main Absent Guest Absent Tom Ward Dr. Harry Cunningham Absent Main Absent Emilia Fox Dr. Nikki Alexander Absent Main David Caves Jack Hodgson Absent Main Liz Carr Clarissa Mullery Absent Main Richard Lintern Dr. Thomas Chamberlain Absent Main Professor Sam Ryan ( Amanda Burton ) -- Series 1 -- 8 . Sam originally lived and worked in Cambridge , but moved to London at the end of series three after she was offered the job of professor at a university . Sam departed in the first episode of series eight , `` A Time To Heal '' . Sam returned home to Ireland after a member of her family was implicated in a murder . Professor Leo Dalton ( William Gaminara ) -- Series 6 -- 16 . Leo first appeared in the episode `` The Fall Out '' , where he was nothing more than a simple doctor . However , he was promoted to professor after former professor Sam Ryan left . In the episode `` Ghosts '' , both his wife , Theresa , and his daughter , Cassie , are killed in a car accident . He began a relationship with fellow professor Janet Mander in `` Death 's Door '' , but ended their relationship in the episode `` Domestic '' . Leo often took a strong opinion on cases and became emotionally involved . He died in the series 16 finale `` Greater Love '' , when he sacrificed himself to save many others from a terrorist bomb explosion . He briefly appeared in a flashback in the last episode of series 20 . Dr. Harry Cunningham ( Tom Ward ) -- Series 6 -- 15 . Harry started out life as a junior doctor , who worked as an apprentice alongside Sam and Leo . However , he soon qualified as a pathologist , and has worked on equal footing with the team for a number of years . Harry was single , and lived alone , but has had several romantic relationships , including an ongoing ' will they - wo n't they ' relationship with his colleague Nikki . Harry left the team to accept a professorship in New York at the end of series 15 . As this was decided after filming was completed , and the stories were reordered , with `` And Then I Fell in Love '' airing last , where it was originally scheduled as the second episode , his departure was never on screen . Dr. Nikki Alexander ( Emilia Fox ) -- since Series 8 . Originally appearing in the episode `` Nowhere Fast '' , Nikki was originally assigned to the Lyell Centre to defuse the tension between Harry and Leo after Sam 's departure . However , Nikki soon became a permanent fixture within the team , and although she features more prominently in the series , holds a lower rank in pathology than Leo . Despite her native home being South Africa , Nikki regards the United Kingdom as her second home , as the reason for her departure from the country lies solely in the hands of her father , Victor , as explained in the episode `` Double Dare '' . Nikki often flirted with colleague Harry , and even invited him to stay at her house after his flat blew up in an explosion . Nikki and Harry were in an ongoing ' will they - wo n't they ' relationship until he left in Series 15 . As well as this , she developed a close relationship with Leo and looked up to him as a father figure . Jack Hodgson ( David Caves ) -- since Series 16 . Before his arrival at the Lyell Centre , Jack was a forensic scientist for the police , working on regular murder investigations . However , when he is called out to the scene of a man 's suspicious death in `` Change '' , both Nikki and Leo spot his potential , and looking for a senior colleague to replace Harry , decide to offer Jack a job as the centre 's forensic expert . Jack is close friends with colleague Clarissa Mullery , whom he invites to work with him at the Lyell Centre , much to Leo 's surprise . In his spare time , Jack is a cage fighter , and splits his home life between forensic research and training for his next fight . Clarissa Mullery ( Liz Carr ) -- since Series 16 . Clarissa is Jack 's personal lab assistant , who first appears in the episode `` Change '' , when Jack invites her to work at the Lyell Centre with him , much to Leo 's surprise . She is a disabled by an unspecified condition and uses an electric wheelchair . She has a very cheeky side , first making a quip at Leo after he fails to recognise who she is on her first arrival . Clarissa had clearly worked for Jack for a long period before his appointment at the Lyell Centre ; however , the exact period of time is unknown . Dr. Thomas Chamberlain ( Richard Lintern ) -- since Series 17 . Thomas Chamberlain has taken over as head of the Lyell Centre from Leo who died at the end of series 16 . He is an experienced forensic pathologist with a renowned reputation in toxicology and is described as charming , charismatic and socially shrewd . His first encounters with Jack , Nikki and Clarissa did not go well but they were gradually warmed to him . It is revealed in the last episode of his first series that his wife has left him just before he started working at the Lyell Centre , and has taken their daughter with her . Professor Sam Ryan ( Amanda Burton ) -- Series 1 -- 8 . Sam originally lived and worked in Cambridge , but moved to London at the end of series three after she was offered the job of professor at a university . Sam departed in the first episode of series eight , `` A Time To Heal '' . Sam returned home to Ireland after a member of her family was implicated in a murder . Professor Leo Dalton ( William Gaminara ) -- Series 6 -- 16 . Leo first appeared in the episode `` The Fall Out '' , where he was nothing more than a simple doctor . However , he was promoted to professor after former professor Sam Ryan left . In the episode `` Ghosts '' , both his wife , Theresa , and his daughter , Cassie , are killed in a car accident . He began a relationship with fellow professor Janet Mander in `` Death 's Door '' , but ended their relationship in the episode `` Domestic '' . Leo often took a strong opinion on cases and became emotionally involved . He died in the series 16 finale `` Greater Love '' , when he sacrificed himself to save many others from a terrorist bomb explosion . He briefly appeared in a flashback in the last episode of series 20 . Dr. Harry Cunningham ( Tom Ward ) -- Series 6 -- 15 . Harry started out life as a junior doctor , who worked as an apprentice alongside Sam and Leo . However , he soon qualified as a pathologist , and has worked on equal footing with the team for a number of years . Harry was single , and lived alone , but has had several romantic relationships , including an ongoing ' will they - wo n't they ' relationship with his colleague Nikki . Harry left the team to accept a professorship in New York at the end of series 15 . As this was decided after filming was completed , and the stories were reordered , with `` And Then I Fell in Love '' airing last , where it was originally scheduled as the second episode , his departure was never on screen . Dr. Nikki Alexander ( Emilia Fox ) -- since Series 8 . Originally appearing in the episode `` Nowhere Fast '' , Nikki was originally assigned to the Lyell Centre to defuse the tension between Harry and Leo after Sam 's departure . However , Nikki soon became a permanent fixture within the team , and although she features more prominently in the series , holds a lower rank in pathology than Leo . Despite her native home being South Africa , Nikki regards the United Kingdom as her second home , as the reason for her departure from the country lies solely in the hands of her father , Victor , as explained in the episode `` Double Dare '' . Nikki often flirted with colleague Harry , and even invited him to stay at her house after his flat blew up in an explosion . Nikki and Harry were in an ongoing ' will they - wo n't they ' relationship until he left in Series 15 . As well as this , she developed a close relationship with Leo and looked up to him as a father figure . Jack Hodgson ( David Caves ) -- since Series 16 . Before his arrival at the Lyell Centre , Jack was a forensic scientist for the police , working on regular murder investigations . However , when he is called out to the scene of a man 's suspicious death in `` Change '' , both Nikki and Leo spot his potential , and looking for a senior colleague to replace Harry , decide to offer Jack a job as the centre 's forensic expert . Jack is close friends with colleague Clarissa Mullery , whom he invites to work with him at the Lyell Centre , much to Leo 's surprise . In his spare time , Jack is a cage fighter , and splits his home life between forensic research and training for his next fight . Clarissa Mullery ( Liz Carr ) -- since Series 16 . Clarissa is Jack 's personal lab assistant , who first appears in the episode `` Change '' , when Jack invites her to work at the Lyell Centre with him , much to Leo 's surprise . She is a disabled by an unspecified condition and uses an electric wheelchair . She has a very cheeky side , first making a quip at Leo after he fails to recognise who she is on her first arrival . Clarissa had clearly worked for Jack for a long period before his appointment at the Lyell Centre ; however , the exact period of time is unknown . Dr. Thomas Chamberlain ( Richard Lintern ) -- since Series 17 . Thomas Chamberlain has taken over as head of the Lyell Centre from Leo who died at the end of series 16 . He is an experienced forensic pathologist with a renowned reputation in toxicology and is described as charming , charismatic and socially shrewd . His first encounters with Jack , Nikki and Clarissa did not go well but they were gradually warmed to him . It is revealed in the last episode of his first series that his wife has left him just before he started working at the Lyell Centre , and has taken their daughter with her . Dr. Trevor Stewart ( William Armstrong ) -- Series 1 -- 3 . As well as being a pathologist in his own right , Trevor was Sam 's business partner , owning half of the morgue and its facilities . Trevor decided to stay in Cambridge with his friends and family when Sam accepted the professorship position at a university in London and moved away at the end of series three . Dr. Fred Dale ( Sam Parks ) -- Series 1 -- 3 . Fred was Sam 's main assistant during post mortems and on visits to crime scenes , often identifying DNA samples at the scene of the crime , and linking them to those responsible . He was also notable for not having many speaking lines , and regularly appearing without speaking . His fate at the end of series three was not revealed . Professor Janet Mander ( Jaye Griffiths ) -- Series 12 -- 15 . Janet is a psychological profiler who assists the police in cases of serial offences . She began a relationship with Leo in the episode `` Safe '' , and they lived together as partners until Leo ended the relationship in `` Redhill '' . She recurringly worked alongside the team to provide them with information in order to get an idea of the suspect they are looking for . Janet decided to move away from London after Leo ended their relationship . Dr. Charlie Gibbs ( Wunmi Mosaku ) -- Series 13 . A junior doctor and lab technician , who was appointed to work with the team by Professor Dalton . Dr. Zak Khan ( Arsher Ali ) -- Series 14 . A junior doctor who worked his forensic science apprenticeship with the team , to learn the ropes of the profession . Wyn Ryan ( Ruth McCabe ) -- Series 1 -- 3 . Professor Ryan 's sister , who , after coming over to visit her from her home in Ireland , ended up living with her on a permanent basis . Ricky Ryan ( Matthew Steer ) -- Series 1 . Wyn 's son and Sam 's nephew , who regularly got into trouble and was expelled from school for very poor behaviour . Rosemary Mason ( Jane Hazlegrove ) -- Series 6 -- 7 . The main receptionist at the Lyell Centre , before the change in focus from university department to purely commercial pathology . Dr. Trevor Stewart ( William Armstrong ) -- Series 1 -- 3 . As well as being a pathologist in his own right , Trevor was Sam 's business partner , owning half of the morgue and its facilities . Trevor decided to stay in Cambridge with his friends and family when Sam accepted the professorship position at a university in London and moved away at the end of series three . Dr. Fred Dale ( Sam Parks ) -- Series 1 -- 3 . Fred was Sam 's main assistant during post mortems and on visits to crime scenes , often identifying DNA samples at the scene of the crime , and linking them to those responsible . He was also notable for not having many speaking lines , and regularly appearing without speaking . His fate at the end of series three was not revealed . Professor Janet Mander ( Jaye Griffiths ) -- Series 12 -- 15 . Janet is a psychological profiler who assists the police in cases of serial offences . She began a relationship with Leo in the episode `` Safe '' , and they lived together as partners until Leo ended the relationship in `` Redhill '' . She recurringly worked alongside the team to provide them with information in order to get an idea of the suspect they are looking for . Janet decided to move away from London after Leo ended their relationship . Dr. Charlie Gibbs ( Wunmi Mosaku ) -- Series 13 . A junior doctor and lab technician , who was appointed to work with the team by Professor Dalton . Dr. Zak Khan ( Arsher Ali ) -- Series 14 . A junior doctor who worked his forensic science apprenticeship with the team , to learn the ropes of the profession . Wyn Ryan ( Ruth McCabe ) -- Series 1 -- 3 . Professor Ryan 's sister , who , after coming over to visit her from her home in Ireland , ended up living with her on a permanent basis . Ricky Ryan ( Matthew Steer ) -- Series 1 . Wyn 's son and Sam 's nephew , who regularly got into trouble and was expelled from school for very poor behaviour . Rosemary Mason ( Jane Hazlegrove ) -- Series 6 -- 7 . The main receptionist at the Lyell Centre , before the change in focus from university department to purely commercial pathology . Superintendent Helen Farmer ( Clare Higgins ) -- Series 1 . A superintendent , and Tom Adams ' boss and mentor , who accompanied him on investigating several cases during his time in the force . Detective Chief Inspector Tom Adams ( John McGlynn ) -- Series 1 . An investigator with the Cambridgeshire police force , who had an affair with Kerry Cox , before her death . Detective Constable Kerry Cox ( Ruth Gemmell ) -- Series 1 . A junior trainee detective who had an affair with Tom Adams , but was later killed in a freak accident in a hospital basement . Detective Constable Marcia Evans ( Janice Acquah ) -- Series 1 . A fellow junior trainee detective for the Cambridgeshire police force , who resigned after Kerry Cox 's death . Superintendent Peter Ross ( Mick Ford ) -- Series 2 . A superintendent , and an ex-boyfriend of Sam 's , who believed in a strong relationship between the police and the pathology lab . Detective Chief Inspector Rachel Selway ( Nicola Redmond ) -- Series 2 . Tom Adams ' replacement , following his resignation from the force . She joined the team alongside junior sergeant Tony Speed . Detective Sergeant Tony Speed ( Richard Huw ) -- Series 2 . A junior sergeant , who joined the team alongside his superior officer , Rachel Selway . He knew Peter Ross from a previous posting . Detective Chief Inspector Michael Connor ( Nick Reding ) -- Series 3 -- 4 . A detective chief inspector , and old friend of Sam 's , whom she met during her junior years at university . Detective Sergeant Rob Bradley ( Mark Letheren ) -- Series 3 . A detective sergeant , who as Connor 's junior officer , accompanied him with the investigating in the cases which he was assigned to . Superintendent Helen Farmer ( Clare Higgins ) -- Series 1 . A superintendent , and Tom Adams ' boss and mentor , who accompanied him on investigating several cases during his time in the force . Detective Chief Inspector Tom Adams ( John McGlynn ) -- Series 1 . An investigator with the Cambridgeshire police force , who had an affair with Kerry Cox , before her death . Detective Constable Kerry Cox ( Ruth Gemmell ) -- Series 1 . A junior trainee detective who had an affair with Tom Adams , but was later killed in a freak accident in a hospital basement . Detective Constable Marcia Evans ( Janice Acquah ) -- Series 1 . A fellow junior trainee detective for the Cambridgeshire police force , who resigned after Kerry Cox 's death . Superintendent Peter Ross ( Mick Ford ) -- Series 2 . A superintendent , and an ex-boyfriend of Sam 's , who believed in a strong relationship between the police and the pathology lab . Detective Chief Inspector Rachel Selway ( Nicola Redmond ) -- Series 2 . Tom Adams ' replacement , following his resignation from the force . She joined the team alongside junior sergeant Tony Speed . Detective Sergeant Tony Speed ( Richard Huw ) -- Series 2 . A junior sergeant , who joined the team alongside his superior officer , Rachel Selway . He knew Peter Ross from a previous posting . Detective Chief Inspector Michael Connor ( Nick Reding ) -- Series 3 -- 4 . A detective chief inspector , and old friend of Sam 's , whom she met during her junior years at university . Detective Sergeant Rob Bradley ( Mark Letheren ) -- Series 3 . A detective sergeant , who as Connor 's junior officer , accompanied him with the investigating in the cases which he was assigned to . During the early years of the show , series creator McCrery wrote and published a number of tie - in novels relating to the series , following Sam Ryan ( Amanda Burton ) and Trevor Stewart ( William Armstrong ) , as well as former main character Superintendent Tom Adams ( John McGlynn ) , and brand new character DS Stanley Sharman , with Burton generally appearing on the front cover of each novel . The fifth novel , due to be published in 2003 , was placed on indefinite hold , and has never been released . Title No . Publication Date `` A Case for the Defence '' 9 September 1996 Walking home from a night out , Sam stumbles upon the remains of a mutilated body on a footpath in the Northwick graveyard . Evidence suggests that the killing may be linked to a particularly ritualistic form of the black arts , but Sam is unconvinced as the murder bears an uncanny resemblance to another murder committed in the same town many years ago . When a second body is discovered , Sam 's evidence is called into question , and is used to create the information that the police need to solve the case , before the killer strikes again . As Sam and Trevor uncover information surrounding the circumstances of the murders , elements that once seemed like coincidences soon appear to belong to a more horrific plan . `` Strange Screams of Death '' 3 August 1998 Sam is tasked with investigating the circumstances surrounding the death of a woman whose body is discovered in a disused shed at a former American airbase on the outskirts of Cambridge . The post mortem reveals that she had been violently raped , before being tortured , and viciously murdered . When a second body is discovered in similar circumstances , Sam finds herself dealing with a serial killer , who has the hunger to slaughter again . Can her profile of information find the identity of the killer before it is too late ? Meanwhile , as Tom Adams closes in on his prime suspect , Sam discovers that he may not be working alone , and a search is launched to find the accomplice of a dangerous criminal . `` The Spider 's Web '' 2 August 1999 Sam is asked to perform a second autopsy on a teenage boy who was killed in a tragic joyriding accident , when despite his parents ' protests , the results of the autopsy seem clear -- he died of multiple injuries consistent with a high - speed car crash . However , as Trevor performed the post mortem , Sam is reluctant to go up against her friend and colleague , in an attempt to find the answers that the family are looking for . However , reading Trevor 's post mortem report prompts Sam to go ahead with the second autopsy , and her findings seem to suggest that the accident may have been no such thing . But neither Trevor nor Superintendent Tom Adams accepts her findings , and believe that she is reading between the lines . `` Faceless Strangers '' 3 September 2001 When the wife and beau of a local member of parliament is found dead in her own home , Superintendent Tom Adams calls upon Sam and the entire resources of the Cambridge Constabulary , in an attempt to further his career , and solve the case as quickly as possible . However , his investigation is halted by the discovery of the decomposed body of a homeless drug addict in the local underground toilet block . When Adams dismisses the death as an open and shut case , one of his juniors , DS Stanley Sharman , decides to enlist Sam 's help , to discover the identity of the dead woman -- and discover just who is responsible for her death . Meanwhile , Adams is determined to crack his case . `` In Search of Evil '' 5 3 November 2003 When the body of elderly widow Violet Thorpe is discovered beneath the floor of her own cellar , Sam quickly establishes that she had been poisoned , and died more than a year prior to the discovery of her body . Meanwhile , the victim 's contact with an old friend living in Brighton , appears to be a vital piece of evdidence in discovering who is responsible for her murder . When Sam and DS Stanley Sharman visit the address of the old friend in Brighton , they find themselves on a bizarre trail of a mentally deranged killer , who appears to be travelling up and down the country in search of lonely old ladies to kill , and Sam finds herself in a race to discover the identity of one of the country 's most prolific serial killers . Title No . Publication Date `` A Case for the Defence '' 9 September 1996 Walking home from a night out , Sam stumbles upon the remains of a mutilated body on a footpath in the Northwick graveyard . Evidence suggests that the killing may be linked to a particularly ritualistic form of the black arts , but Sam is unconvinced as the murder bears an uncanny resemblance to another murder committed in the same town many years ago . When a second body is discovered , Sam 's evidence is called into question , and is used to create the information that the police need to solve the case , before the killer strikes again . As Sam and Trevor uncover information surrounding the circumstances of the murders , elements that once seemed like coincidences soon appear to belong to a more horrific plan . `` Strange Screams of Death '' 3 August 1998 Sam is tasked with investigating the circumstances surrounding the death of a woman whose body is discovered in a disused shed at a former American airbase on the outskirts of Cambridge . The post mortem reveals that she had been violently raped , before being tortured , and viciously murdered . When a second body is discovered in similar circumstances , Sam finds herself dealing with a serial killer , who has the hunger to slaughter again . Can her profile of information find the identity of the killer before it is too late ? Meanwhile , as Tom Adams closes in on his prime suspect , Sam discovers that he may not be working alone , and a search is launched to find the accomplice of a dangerous criminal . `` The Spider 's Web '' 2 August 1999 Sam is asked to perform a second autopsy on a teenage boy who was killed in a tragic joyriding accident , when despite his parents ' protests , the results of the autopsy seem clear -- he died of multiple injuries consistent with a high - speed car crash . However , as Trevor performed the post mortem , Sam is reluctant to go up against her friend and colleague , in an attempt to find the answers that the family are looking for . However , reading Trevor 's post mortem report prompts Sam to go ahead with the second autopsy , and her findings seem to suggest that the accident may have been no such thing . But neither Trevor nor Superintendent Tom Adams accepts her findings , and believe that she is reading between the lines . `` Faceless Strangers '' 3 September 2001 When the wife and beau of a local member of parliament is found dead in her own home , Superintendent Tom Adams calls upon Sam and the entire resources of the Cambridge Constabulary , in an attempt to further his career , and solve the case as quickly as possible . However , his investigation is halted by the discovery of the decomposed body of a homeless drug addict in the local underground toilet block . When Adams dismisses the death as an open and shut case , one of his juniors , DS Stanley Sharman , decides to enlist Sam 's help , to discover the identity of the dead woman -- and discover just who is responsible for her death . Meanwhile , Adams is determined to crack his case . `` In Search of Evil '' 5 3 November 2003 When the body of elderly widow Violet Thorpe is discovered beneath the floor of her own cellar , Sam quickly establishes that she had been poisoned , and died more than a year prior to the discovery of her body . Meanwhile , the victim 's contact with an old friend living in Brighton , appears to be a vital piece of evdidence in discovering who is responsible for her murder . When Sam and DS Stanley Sharman visit the address of the old friend in Brighton , they find themselves on a bizarre trail of a mentally deranged killer , who appears to be travelling up and down the country in search of lonely old ladies to kill , and Sam finds herself in a race to discover the identity of one of the country 's most prolific serial killers .
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