Penned by Mark Gatiss, 'The Hounds of Baskerville' is a modern-day update of Conan Doyle's classic 1902 novel and features a guest appearance from Russell Tovey.
In the new video preview, Sherlock (Benedict Cumberbatch) scoffs at rumours of a "super dog" prowling the wilds of Dartmoor, but his interest is soon piqued by a compelling piece of evidence.
Sherlock continues on Sunday at 8.30pm on BBC One.
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Watch a clip from Sherlock 'The Hounds of Baskerville' below: