A Study In Pink
The police investigate the deaths of a series of people who all appear to have committed suicide by taking a poisonous pill. They turn to their unofficial consultant, Sherlock Holmes, who deduces various elements pointing to a serial killer. Meanwhile, Sherlock Holmes is introduced to John Watson, a former soldier who served in Afghanistan, and the pair immediately move into a flat in Baker Street. John Watson slowly gets to know and trust Holmes despite police officer Sally Donovan (Vinette Robinson) warning him that Holmes is a psychopath and will one day be responsible for murder. Sherlock's brotherMycroft (Mark Gatiss), at first not revealing his identity, kidnaps Watson and asks whether he'll spy on Sherlock for money, but Watson refuses. After a series of incidents, the person responsible for the deaths, a taxicab driver (Phil Davis), reveals that his victims took their own lives by playing a game of Russian roulette with two pills: one fatally poisonous, the other safe. Watson shoots the cabbie, who reveals as he dies that Moriarty was his sponsor.
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 the gang is in communication with her superior, who is identified by the initial "M". She is then shot by a sniper.
The Great Game
Holmes is commissioned by Mycroft to investigate the suspicious death of a government employee, who was working on a top-secret defence project: the Bruce-Partington Project. After apparently rejecting the case and handing it over to Watson, Holmes begins to be taunted by a criminal who puts his victims into explosive vests and sets Holmes deadlines to solve the apparently unrelated cases, which include a twenty-year-old cold case involving the shoes of a drowned boy, the disappearance of a businessman, the death of a TV personality, and the assassination of a guard of an art gallery by the "Golem". As Holmes solves the cases, he finds links between them. After clearing up the original case of the civil servant, Holmes tries to force his unseen adversary to reveal himself. Near the end of the episode, Holmes and "Jim Moriarty" reach a standoff, where Jim reveals that he is responsible for the crimes. In the final seconds, Sherlock Holmes points his gun at a bomb on the floor that was strapped to Watson.
A Scandal In Belgravia
Mycroft hires Holmes and Watson to retrieve compromising photos of a minor royal, which are held on Irene Adler's (Lara Pulver) camera phone, a ruthless and brilliant dominatrix who also trades in classified information extracted from her rich and powerful clients. Holmes obtains Adler's phone, but discovers it is booby-trapped and requires a code to disarm it. When Adler discovers that the CIA are on her trail, she disappears and is then apparently killed, only to reappear weeks later when the coast is clear. Adler manipulates Holmes into deciphering a coded message on her phone which she obtained from another well-connected client. She sends the message to Moriarty, who in turn uses it to foil a British counter-terror operation, before going underground again. The episode concludes as Mycroft tells Watson that she has been killed by a terrorist group in Pakistan. This is another lie: Sherlock helped her escape when she was on the brink of death.
The Hounds Of Baskerville
Sherlock and Watson are contacted by Henry Knight (Russell Tovey), a man traumatized by the death of his father by a monstrous hound on Dartmoor years before. Investigating Dewer's Hollow, a local spot where the beast was allegedly seen, as well as the nearby Ministry of Defence testing site Baskerville, Holmes and Watson uncover a conspiracy wherein one of the Baskerville scientists, Dr. Frankland (Clive Mantle), is continuing the work of H.O.U.N.D., an aborted project to create a hallucinogenic gas for military use. Holmes and Watson discover that the legendary hound is an ordinary dog used for publicity that the hallucinogenic gas makes appear as a demonic monster. The "hound" that killed Henry's father was actually Frankland wearing a red-lensed gas mask and a T-shirt bearing the logo of the H.O.U.N.D. group. Confronting both the dog and Frankland at Dewer's Hollow, Watson and Lestrade shoot the dog. Frankland attempts to flee, but dies when he runs into a minefield. In the final scene, Mycroft releases a confined Jim Moriarty.
The Reichenbach Fall
After a series of high-profile cases lead Sherlock to fame, Moriarty launches a simultaneous heist on the Tower of London, Bank of England and Pentonville Prison, for which he allows himself to be captured and put on trial. He secures a not-guilty verdict through blackmailing the jury and visits Holmes, explaining he still intends to "burn" him, taunting him with a "final problem" for him to solve. Soon afterwards, Moriarty arranges for the kidnapping of the children of an American ambassador, who are terrified of Holmes once he has them rescued. This, in conjunction with the ease with which Sherlock solves the case, leads to Holmes becoming a suspect. Holmes escapes arrest, and soon learns Moriarty is under the alias of an actor hired by Holmes, and has seeded the press with a story of Holmes being a fraud. The two meet on the roof of a hospital, where Moriarty explains that assassins will kill Watson, Mrs. Hudson and Lestrade if Sherlock Holmes does not commit suicide; he wants Holmes to do this to cement his story. After a tense conversation, in which Moriarty realizes the two are enough alike that Sherlock could extract the code to call off the assassins from him, Moriarty shoots himself instead. Sherlock calls Watson and "confesses" to being a fraud (which Watson refuses to believe). Watson pleads for him to come down. Sherlock states his final "Goodbye" and then steps off the roof, leading to hisvilification by the press. Watson and Mrs. Hudson meet alone at Sherlock's grave to say their goodbyes; the final seconds show Sherlock watching from afar, having faked his death. Moffat and Gatiss have stated that it was shown on screen how he survived, but that no one has yet figured it out.
Season 3 (coming soon)
As they had to promote series two, Moffat and Gatiss announced three words to tease the content of the third series. These words were, "rat, wedding, bow". Speaking at the Edinburgh International Television Festival in August 2012, Moffat said that these words "may be misleading, are not titles, are only teases or possibly clues, but might be deliberately designed to get you into a lather. The third series, again written by Moffat, Gatiss and Thompson, is scheduled to start filming in March 2013.The first episode will be based on "The Adventure of the Empty House" and will be written by Gatiss.