Planning Scott’s stag night is a headache for Jason. Karen shares a secret with Nikki. Erica and Freddy’s relationship begins to blur.

Holmes and Watson travel to Europe to escape Moriarty’s vengeance.

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…

Sherlock faces perhaps the most chilling enemy of his long career: the powerful and seemingly unassailable Culverton Smith – a man with a very dark secret indeed.