Last updated 24 March 2024


Episode 4

Series Episode Number: 275

World Premiere: Sat 30 May 1970 - 5:15pm BST [BBC One] (United Kingdom)
First Broadcast: Mon 3 Nov 1975 - 6:30pm CST [WTTW 11 Chicago]
Running Time: 24 minutes 57 seconds

6.00 Million (UK)

Appreciation Index: 60 (UK)

Chart Position: 54 () (UK)

Recorded on Fri 08 May 1970 in TC3 / TC6
Archive State: RSC conver



In the parallel world, the drilling project is about to penetrate Earth's crust. The Doctor, arrested as a spy, is unable to convince his captors of the danger that faces them.


Production Team hide uncredited
WriterDon Houghton
DirectorDouglas Camfield
ProducerBarry Letts
DesignerJeremy Davies
Script EditorTerrance Dicks
Film CameramanFred Hamilton
Film SoundGraham Hare
Film EditorMartyn Day
Visual Effects DesignerLen Hutton
Title MusicRon Grainer
and BBC Radiophonic Workshop
CostumesChristine Rawlins (uncredited)
Make-upMarion Richards (uncredited)
Studio LightingJohn Green (uncredited)
Studio SoundJohn Staple (uncredited)
Special SoundBrian Hodgson (uncredited)
Technical ManagerRay Hider (uncredited)
Vision MixerJohn Gorman (uncredited)
Grams OperatorTony Philpott (uncredited)
Production AssistantChris D'Oyly-John (uncredited)
Assistant Floor ManagerSue Hedden (uncredited)
Floor AssistantFrank Mullan (uncredited)
Make-Up AssistantJudy Cain (uncredited)
Make-Up AssistantSue Duckworth (uncredited)
Make-Up AssistantIrene Walls (uncredited)
Scene CrewBrian Mitchell (uncredited)
Scene CrewBrian West (uncredited)
Costume AssistantTerry Styles (uncredited)
Costume AssistantPat Trigger (uncredited)
Film Camera AssistantHugh Miles (uncredited)
Film Sound AssistantJack Curtis (uncredited)
Director's AssistantSue Upton (uncredited)
Title Music ArrangerDelia Derbyshire (uncredited)
Title SequenceBernard Lodge (uncredited)