A woman in pink lies dead in a derelict house. She is the fourth in a series of seemingly impossible suicides. DI Lestrade is the best Scotland Yard has got, but even he knows that there's only one man who can help. Elsewhere in London, a war hero, invalided home from Afghanistan, meets a strange but charismatic genius who is looking for a flatmate; Dr John Watson and Sherlock Holmes are meeting for the first time.