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The episode will last for 45 minutes, and finishes at 8.05pm. Knock Knock, written by new writer Mike Bartlett, will air on the same day on BBC America at 9/8C.
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?