 A new principal character, Jack Turner (Michael Kitchen), was introduced at the start of the series to act as a catalyst between Christine and Robert.Jane Danson was also introduced as new regular cast member Samantha Docherty.Following the loss of a large chunk of the main cast, the fourth series saw the introduction of twelve new characters, including new senior doctors Ruth Cole (Jaye Griffiths) and Danny Barton (James Murray), with only four of the show's original stars returning.