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

Cast: Benedict Cumberbatch, Martin Freeman, Amanda Abbington, Asheq Akhtar, Usman Akram, Sharon Cherry Ballard, Louise Brealey, Miranda Hennessy, Toby Jones, Lee Kemp, David Kirkbride, Tom Williams, Chris Wilson