The doctor and Clara find themselves on a Russian cold war submarine that is falling to the bottom of the ocean because of an attack by a rogue Martian warrior, that 's still aboard.
Episode rating
Cast of episode
78
17
- Clara
- The Doctor
- Captain Zhukov
- Professor Grisenko
- Lieutenant Stepashin
- Piotr
- Onegin
- Belevich
- Creature Movement
- Daleks
- Submariner
- 80s Man