The Doctor attempts to persuade Captain Hart of the danger that the Master represents. Eager to make contact with the Sea Devils, the Doctor journeys deep into the ocean.
Share this with
See all episodes from Doctor Who
See all clips from Part 4
See all broadcasts of Part 4 (2)
Check out the best of the latest news and photos from our Twitter and Instagram accounts!
The Doctor (Peter Capaldi) answers the age old question in this must-see video!
More levels! More adventure! And it’s now available on tablets!
Available on: DVD
From suppliers including: Amazon, BBC Shop
Where to buy
See all galleries from Part 4