who is the writer of the episode?
Mark Gatiss
The Hounds of Baskerville
 It was written by co-creator Mark Gatiss, 
whatt is "the hounds of baskerville"? Second episode of the second series of the BBC crime drama series "Sherlock" when was it released? 8 January 2012
wiki:19769761
The Hounds of Baskerville [SEP] Introduction
"The Hounds of Baskerville" is the second episode of the second series of the BBC crime drama series "Sherlock", which follows the modern-day adventures of Sherlock Holmes, and was first broadcast by BBC One on 8 January 2012. It was written by co-creator Mark Gatiss, who also portrays Mycroft Holmes, Sherlock's brother in the series, and was directed by Paul McGuigan. The episode is a contemporary adaptation of "The Hound of the Baskervilles", one of Sir Arthur Conan Doyle's most famous works. In the episode, Sherlock (Benedict Cumberbatch) and his crime-solving partner John Watson (Martin Freeman) take on the case of Henry Knight (Russell Tovey), who 20 years earlier witnessed the brutal killing of his father by a "gigantic hound" on Dartmoor.