Part One
Series Episode Number: 402World Premiere: Sat 30 Aug 1975 - 5:46pm BST [BBC One] (United Kingdom)
First Broadcast: Tue 25 Mar 1980 - 5:30pm CST [WTTW 11 Chicago]
Running Time: 21 minutes 41 seconds
8.40 Million (UK)
Appreciation Index: 59 (UK)Chart Position: 29 () (UK)
Recorded on Mon 07 Apr 1975 in TC3 at these locations
BBC Genome Project: see entry
The Doctor, Sarah and Harry return to Earth to help the Brigadier discover what is causing the destruction of oil rigs off the coast of Scotland.