On the planet Marinus, the Doctor and his companions are enlisted by Arbitan to seek out the keys to an ancient and powerful machine. Their quest takes them across time and space; will they be able to return the keys before Marinus falls under the control of the alien Voord? (Originally broadcast in six parts.)
Did You Know?
This episode was watched by 9.9 million viewers on its original transmission. See more
When Ian is first inside the pyramid, someone stumbles through the background. See more
Then everything out there is acid. A sea of acid.