The Doctor, Tegan and Turlough arrive on an underwater sea base in 2084 where they are accussed of being spies and saboteurs. The sea base is set to monitor a rival power bloc, and the crew regularly test their missiles to ensure they will be ready if they are called upon.
Underneath the sea a Silurian triad has survived, and they revive a colony of Sea Devils to attack the base. Icthar, the leader of the Silurians, aims to fire the base's missiles at the rival power bloc which would provoke a global nuclear war and kill all life on Earth. The Silurians would then emerge as the rightful inhabitants.
The base has in storage canisters of hexachromite gas which is lethal to all reptiles. Reluctantly the Doctor agrees to the use of the gas to kill the Sea Devils and Silurians while he disables the sea base's missiles.
Regular castTegan Jovanka: Janet Fielding; Vislor Turlough: Mark Strickson;
Guest castCommander Vorshak: Tom Adams; Lieutenant Bulic: Nigel Humphreys; Lieutenant Preston: Tara Ward; Icthar: Norman Comer; Scibus: Stuart Blake; Tarpok: Vincent Brimble; Sauvix: Christopher Farries; Paroli: James Coombes (1-3); Doctor Solow: Ingrid Pitt (1-3); Controller Nilson: Ian McCulloch (1-3); Lieutenant Maddox: Martin Neil (1-3); Lieutenant Karina: Nitza Saul (1-3);
Uncredited cast: Double for the Doctor: Gareth Milne (1-2); The Myrka: John Asquith (2-3), William Perrie (2-3); Sea Devils: Mike Braben, Steve Kelly, Dave Ould, Jules Walters, Chris Wolfe; Marine Guards: Peter Caton, Ridgewell Hawkes, Julian Hudson, Julian Larousse, Barney Lawrence, Dana Miche, Dorothy Ottey, Rose Pridmore, Trevor Steedman; Base Personnel: Russell Brook, Joanna Garcia, Joyce Goburn, Arnold Lee, Ling Tai;
|BBC 1||603||Part One||Thu 5 January 1984||6:40 pm - 7:05 pm||7.6M||51st|
|BBC 1||604||Part Two||Fri 6 January 1984||6:40 pm - 7:05 pm||7.5M||52nd|
|BBC 1||605||Part Three||Thu 12 January 1984||6:40 pm - 7:05 pm||7.3M||74th|
|BBC 1||606||Part Four||Fri 13 January 1984||6:40 pm - 7:05 pm||6.6M||87th|
Royal Engineers Diving Establishment, McMullen Barracks, Marchwood, nr. Southampton, Hants;
Shepperton Stage A; Television Centre Studio 6;
Bloopers and mistakes
The Silurian costumes come apart in places, and white T-shirts can be seen through the holes! (This story fell more behind production schedule than any other and apparently some takes were, as far as the actors knew, just full-dress rehearsal.)
Episode 4: Watch the scene where Doctor is standing on the Bridge as some Sea-Devils exit behind him. Two of them manage to walk straight into each other.
Notes and trivia
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