Parts: 1 (45-minute)
Writers: Peter Harness
Airdate: 04 October 2014
Production Code: n/a

Doctor: twelfth
Companions: Clara, Courtney

Story: In an effort to cheer up Courtney, the Doctor offers to take her to the moon, so that she can be the first woman to set foot on its surface. Instead of landing on the moon directly, though, the TARDIS materializes onboard a rickety old space rocket that's about to make a crashlanding on the moon... with one hundred nuclear bombs on board.

The rocket is crewed by three astronauts who have come to the moon with the mission of discovering what happened to a mineralogical survey team that dropped out of contact ten years ago. As the Doctor soon discovers, the moon has a higher gravity than it ought to, which has been wreaking havoc on the Earth's tides and satellites since the miners landed. In order to save the Earth, the Doctor and his friends must discover what's affecting the moon's gravity... but saving the Earth may require the sacrifice of an innocent life.