This story is based on the actual murder of actor-manager William Terriss by Richard Prince outside London's Adelphi Theatre on 16 December 1897.

First transmitted 27 February 2002, this story is based on a reference from Doyle's novel The Sign of the Four: "I assure you that the most winning woman I ever knew was hanged for poisoning three little children for their insurance-money..." Holmes recalls a case from his past when the guidance of an extraordinary man helped solve a particularly diabolic crime.

Holmes and Watson can rarely have been faced with such an uncooperative and unusual client, and they have just forty minutes to find out what problem has brought him to 221B Baker Street before the heavy boots of the official police force start clumping up the stairs.

Charlotte Adams is young, idealistic and happily absorbed in her volunteer work among the poor and suffering of the East End.

First transmitted on 15 June 2004, this story is based on a reference from Doyle's novel The Hound of the Baskervilles: "Since the tragic upshot of our visit to Devonshire [Holmes] had been engaged in two affairs of the utmost importance, in the first of which he had exposed the atrocious conduct of Colonel Upwood in connection with the famous card scandal of the Nonpareil Club."

A body in Hyde Park and a potential scandal at an exclusive gambling club bring Holmes back into contact with a beguiling but most notorious former client.

A night at the music hall ends in death, a Wild West sharpshooter finds a new personality, a brick wall crumbles and Holmes is engaged by a most unexpected client.

Additional cast First transmitted on 2 January 2009, this story is based on a reference from Doyle's novel The Hound of the Baskervilles: "'Ah, Wilson, I see you have not forgotten the little case in which I had the good fortune to help you?

A series of inexplicable and bizarre incidents on a non-stop express train brings a railway baron to Baker Street and takes Holmes and Watson to Rugby.

The detective gets a chance to use one of his less frequently aired foreign languages, the doctor gets the shock of his life, a policeman becomes a suspect, a brass band plays a part, and the safety of the Empire is secured by a remarkable bird... Holmes refers to this case in the Series Two adventure "The Abergavenny Murder", calling it "The lighthouse, the politician and the trained cormorant ... tedious little case, that."

The enigmatic Mycroft Holmes astonishes his brother as the shocking truth behind the mystery of the politician, the lighthouse and the trained cormorant is finally revealed.