A Study In Pink

Doctor watson an army doctor,was injured in Afghanistan, meets Sherlock Holmes (Benedict Cumberbatch) who is looking for a flatmate to share a flat at 221B Baker Street, owned by landlady Mrs. Hudson (Una Stubbs). The police, led by Detective Inspector Lestrade (Rupert Graves), have been baffled by a strange series of deaths, which he can only describe as "serial suicides". Sherlock looks at the latest crime scene, of a woman named Jennifer Wilson who was dressed in pink. Sherlock deduces Wilson was a serial adulterer in an unhappy marriage. Unlike other victims, she left a note, clawing "Rache" into the floor. Sherlock ignores forensic expert Anderson's suggestion that it is German for "revenge" and reckons the victim died before finishing to write "Rachel". Sherlock finds splashes of mud on her leg, thrown up by the wheel of a suitcase, and deduces she is from out of town. The police found no suitcase with the body, but Sherlock searches for it later, finding it abandoned nearby. Meanwhile, John receives a call in a telephone box and is taken to an empty warehouse, where he meets a man who claims to be Sherlock's "arch-enemy". He offers him money to spy on Sherlock, but John refuses. The man also tells John that far from suffering from post-traumatic stress disorder as his therapist believes, he actually misses the war.

When John returns to 221B, Sherlock asks him to send a text message to Wilson's still-missing phone, hoping the murderer will make a move. While waiting at a local restaurant, Sherlock notices a cab and gives chase, using his extensive knowledge of London's streets and alleys, to outpace it on foot. However, when they finally stop the cab, the passenger is a tourist from North America who has just arrived in the United Kingdom: a perfect alibi. Believing Sherlock withheld evidence, Lestrade executes a drugs bust as an excuse to search his flat. Sherlock presumes "Rachel" was Wilson's e-mail password and the victim planted her phone on the killer so he could be traced by GPS. At the same time John finds the signal is coming from 221B, Mrs. Hudson tells Sherlock a taxi is waiting for him. Outside, the cabbie (Phil Davis) confesses to the killings, but proclaims he merely speaks to his victims and they kill themselves. He challenges Sherlock to solve his puzzle, and later, inside a quiet college building, the cabbie pulls out two bottles, each containing an identical pill. He says one of the pills is harmless, the other poison; he invites his victims to choose one, promising he will swallow the other — and he will simply shoot them if they refuse.

Sherlock soon deduces the cabbie is an estranged father who was told 3 years earlier he was dying. The cabbie admits that a "fan" of Sherlock's contacted him and offered to "sponsor" his work, paying money for each murder, to be left to the cabbie's children. Sherlock realises the gun is actually a novelty cigarette lighter and starts to leave. However, the cabbie challenges him again to choose a pill and see if he can solve the puzzle. Meanwhile, John traced the GPS signal from the phone and followed Sherlock. Through a window in the adjacent building he shoots the cabbie. Sherlock questions the dying cabbie about the identity of his "fan", the cabbie's sponsor, and finally, under duress, he reveals a name: "Moriarty". The police arrive and Sherlock starts deducing facts about the shooter's identity, before realising it must be John and telling Lestrade to ignore everything he said. Sherlock and John leave the scene and run into the man who had abducted John earlier. He turns out to be Sherlock's elder brother, Mycroft(Mark Gatiss); John now understands why Mycroft tried to bribe him out of genuine concern for Sherlock. Mycroft then instructs his secretary Anthea (Lisa McAllister) to increase their surveillance status.