Part TwoSeries Episode Number: 573
World Premiere: Tue 9 Mar 1982 - 7:05pm GMT [BBC One: Not Wales] (United Kingdom)
Running Time: 24 minutes 23 seconds
8.80 Million (UK)
Chart Position: 50 () (UK)
With her crew vanishing mysteriously, Captain Briggs assumes the Doctor is the guilty party, but the traitor is closer to home as are the Cybermen.