The official story synopsis for Knock Knock, the fourth episode of Series 10, has been released by the BBC:

Bill is moving in with some friends and they’ve found the perfect house – so what if it’s strangely cheap to rent, and the landlord is a little creepy?

The wind blows, the floorboards creak, and the Doctor thinks something is very wrong. What lurks in the strange tower at the heart of the building – and why can’t they find any way to enter it?

The Doctor is played by Peter Capaldi, Bill by Pearl Mackie and Nardole by Matt Lucas. David Suchet guest stars at the Landlord.

Please note: a special binaural audio edition of this episode will be available on BBC iPlayer immediately after it is broadcast on TV. This creates a 3D surround sound effect for anyone wearing headphones, placing them at the heart of the action in this nail-biting episode.