Last updated 24 March 2024

Part One

Series Episode Number: 603

World Premiere: Thu 5 Jan 1984 - 6:41pm GMT [BBC One] (United Kingdom)
First Broadcast: Fri 7 Dec 1984 - 11:00pm CST [WTTW 11 Chicago]
Running Time: 24 minutes 48 seconds

7.60 Million (UK)

Appreciation Index: 65 (UK)

Chart Position: 51 () (UK)

Seabase 4 is on alert as a strange craft approaches. But the crew has been infiltrated by the enemy, so Commander Vorshak's solutions are scuppered at every turn.

Production Team include uncredited
WriterJohnny Byrne
DirectorPennant Roberts
ProducerJohn Nathan-Turner
DesignerTony Burrough
Script EditorEric Saward
Title SequenceSid Sutton
Costume DesignerJudy Pepperdine
Make-up ArtistJennifer Hughes
LightingPeter Smee
SoundMartin Ridout
Technical ManagerAlan Arbuthnott
Camera SupervisorBob Baxter
Camera SupervisorAlec Wheal
Videotape EditorHugh Parson
Visual Effects DesignerMat Irvine
Video EffectsDave Chapman
Vision MixerNigel Finnis
Technical Manager(TM2)Alan Woolford
OB Camera SupervisorAlastair Mitchell
OB SoundChris Holcombe
Production ManagerMichael Darbon
Production AssociateJune Collins
Production AssistantNorma Flint
Assistant Floor ManagerAdrian Hayward
Incidental MusicJonathan Gibbs
Special SoundDick Mills
Title Music BBC Radiophonic Workshop
Special Sound BBC Radiophonic Workshop