Benedict Cumberbatch and Martin Freeman star in a special edition of the cult crime drama which sees Holmes and Watson travel back in time to Victorian London, where a man is haunted by the ghost of his wife.
The spellbinding 2016 special that acted as a bridge between Series 3 and Series 4.
Find out more about the actor who plays the genius detective Sherlock Holmes.
Find out more about the actor who plays Dr. John Watson.