Imagining himself back in the 1890s, Sherlock is visited by Inspector Lestrade after newlywed Emelia Ricoletti, having apparently killed herself in public, murders her husband Thomas in front of witnesses before vanishing. Some months later Holmes is approached by Lady Carmichael, who tells him that her husband Sir Eustace has been threatened by Emelia, who then seemingly does away with him. With an intrusive Moriarty crossing him, Holmes attempts to solve the enigma, with unexpected help from Watson's wife Mary and evidence of a conspiracy involving half the population of the country. Written by don @ minifie-1

Sherlock waits to see where Moriarty will make his posthumous move. One mysterious case in particular baffles Scotland Yard but Sherlock is more interested in a seemingly trivial detail. Why is someone destroying busts of the late Prime Minister Margaret Thatcher? Is there a madman on the loose, or is there a much darker purpose at work, something with its roots deep in Mary Watson's past?

As Sherlock attempts to comfort John Watson after his wife's death, entrepreneur and apparent philanthropist Culverton Smith tests a new drug on his employees and his daughter Faith to make them forget his confession that he plans to commit murder. Faith retains a partial memory and approaches Sherlock to identify a likely victim but her disappearance, and his descent into drug abuse, lands him in Smith's hospital and at his mercy. Though Sherlock is not as helpless as he appears and has his own way of trapping Smith, the final shock is reserved for Watson as his new therapist springs a terrible surprise on him. Written by don @ minifie-1

Long-buried secrets finally catch up with the Baker Street duo. Someone has been playing a very long game indeed and, alone and defenseless, Sherlock and Dr Watson face their greatest ever challenge. Is the game finally over? Written by BBC One