Earth in the 21st Century enjoys the T-Mat, a form of instantaneous matter transport system which has replaced all other forms of transport on earth. The system is controlled from Earth, with one of its main relay stations located on the Moon. The machine breaks down and the Doctor and Gia Kelly, the technical brains behind the system, go to the Moon to investigate. They find the Moon overrun by Ice Warriors, who are preparing to launch an invasion against Earth.  To weaken Earth's resistance they are using the T-Mat to send Martian Seed Pods, which will emit a lethal fungus, over Earth's winter zones. The Doctor manages to use the T-Mat to return to a chaotic Earth, where the Ice Warriors have managed to take control of the weather. The Doctor finds that the only thing that can destroy the fungus is heavy rains and warmth, which he provides after regaining control of the weather station. A solar heat gun takes care of the remaining Ice Warriors.  
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The Doctor: Patrick Troughton
Jamie McCrimmon: Frazer Hines
Zoe Heriot: Wendy Padbury

Guest Appearances:
Slaar: Alan Bennion
Ice Warriors: Steve Peters, Tony Harwood, Sonny Caldinez
Eldred: Philip Ray
Gia Kelly: Louise Pajo
Computer Voice: John Witty
Brent: Ric Felgate
Osgood: Harry Towb
Radnor: Ronald Leigh-Hunt
Fewsham: Terry Scully
Phipps: Christopher Coll
Locke: Martin Cort
Guard: Derrick Slater
Marshal: Graham Leaman
Sir James Gregson: Hugh Morton
Weather Station:Operator: Peter Whittaker

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Producer: Peter Bryant.
Script Editor: Terrence Dicks.
Writer:   Brian Hayles with Terrence Dicks Uncredited. 
Director: Michael Ferguson.
Designer: Paul Allen. 
Costume:  Bobi Bartlett.
Make up: Sylvia James.
Visual Effects:  Bill King and 'Trading Post'
Music : Dudley Simpson.
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Novelised as "Doctor Who - The Seeds of Death" by Terrence Dicks  (0 426 20252 X) first published by  W.H. Allen (now Virgin Publishing Ltd.) in 1986 with cover by Tony Masero.  Target library number 112.

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Released on Video as "The Krotons" both as VHS & Betamax (BBCV 2019 / 4072) first released in 1985 with photomontage cover. Also released in Australia & New Zealand (BBC catalogue #4072) and in US & Canada in 1990 (CBS/FOX catalogue #3716)

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Terrence Dicks reworked the final four episodes as the original scripts were not what the production office required.
Patrick Troughton does not appear in episode four as he was on holiday during its filming.

All six episodes exist as 16mm telerecordings, though a 35mm telerecording of episode five also exists. All episodes except part three were held by the Film & TV Library when audited in 1978.

Ealing Film Studio Stage 2. (13, 16-18, 20, 23 December 1968)
Studio recording in Lime Grove D. (3, 10, 17, 24, 31 January; 7 February 1969)
Hampstead Heath Extension, West Heath Road, Hampstead, London, NW3. (19 December 1968)

Episode 1, 2 - In episode 2, Fewsham tells Miss Kelly that Osgood killed Locke when he tried to fuse the controls, but back in episode 1, Locke told Radner and Miss Kelly that it was Osgood who died.
Episode 2 - The microphone is out of range when Miss Kelly gives her line about having enough fuel reserves to reach the moon.
Episode 3 - In the storeroom, when Zoe says "I think I heard something", she opens the door to the sight of an Ice Warrior standing right outside the door. But when we cut to a shot from the corridor showing Zoe looking out, the Ice Warrior has magically teleported itself several yards down the corridor and is facing the other way!
Episode 4 - Phipps lifts Zoe up too high to get through the air vent,and she bumps her head.
Episode 5 - When Eldred points to the Weather Control Bureau on a map, notice that it's actually in the opposite corner of the map to the one he's pointing to.
Episode ? - The Doctor's hair goes through remarkable changes in length and thickness throughout the course of the story. An example: He finds out Radner hasn't received the message to make it rain, and comes to the conclusion that Jamie and Zoe have gone to the weather control centre themselves. Radner then says that this was where the Ice Warrior was last seen and the Doctor rushes out. Outside, the Doctor is running fast, and his hair is suddenly an awful lot shorter!
Episode ? - Watch the scene in the storage room where Jamie is fighting with an Ice Warrior. At some point one of them knocks against the wall, and it wobbles quite distinctly.
Episode ? - Watch for when one of the crew on the Moonbase is attacked by the Ice Warrior. He collapses across the main control console, which wobbles like a piece of cardboard, amazingly enough.
Episode ? - When the Doctor enters the Weather Control Building (which is full of suds), he and Zoe race down a corridor, then stop and talk for a few seconds. They then start to rush off to find Jamie when Zoe says, "No, this way" and points. Wendy Padbury starts going in that direction but slips on the mess of suds that is all over the floor. She bumps into the Doctor (who is also having balancing problems) almost knocking him over in the process... Finally, they both stagger off the screen. Pure slapstick!
Episode ? - Take a look at one of the Ice Warriors approaching the Weather Control station. There is a head-and-shoulders shot in which several strands of long black hair are sticking out from beneath the back of his helmet...
Episode ? - Watch carefully for the scene where Zoe's pants are falling down. She's in the background and looks very silly!
Episode ? - During the scene in the space museum when they're building the rocket, you can distinctly hear the sound of a wrench (or some other metal tool) being dropped on the cement floor.
Episode ? - Zoe refers to Slaar by name, though no other characters seem to know his name, and never mention it.