Sherlock: Season 1, Episode 2

1 - 2: The Blind Banker

Holmes is hired by an old friend to investigate a mysterious break-in at a bank in the City. He discovers that symbols spray-painted onto an office wall are a coded message intended for an employee of the bank, who is later discovered dead in his flat. The next day, a journalist is killed and the same symbols are found nearby. Holmes and Watson follow a trail of clues that link the two dead men to a Chinese smuggling ring, who are trying to retrieve a valuable item that one of them stole. Holmes eventually cracks the coded message based on Suzhou numerals and a book cipher, but not before Watson and a female friend are kidnapped by the criminals. Holmes rescues Watson's friend but the leader of the gang escapes. After escaping, the leader of gang is in communication with her superior, who is identified by the initial "M". She is then shot by a sniper.