Part FourSeries Episode Number: 477
World Premiere: Sat 25 Feb 1978 - 6:25pm GMT [BBC One] (United Kingdom)
First Broadcast: Thu 14 Feb 1980 - 5:30pm CST [WTTW 11 Chicago]
Running Time: 23 minutes 31 seconds
10.90 Million (UK)
Chart Position: 28 () (UK)
Recorded on Sun 06 Nov 1977 in TC8
As the Vardans finally fully materialise on Gallifrey, the Doctor prepares to spring his trap. But does a more deadly alien force lie behind the Vardans?