Original air dates 29 January – 19 February 1977.
A large vessel with a part human and part robot crew is doing something. There is some mistrust of the robots, for all that they’re in critcal positions everywhere. Politics appears to be rampant.
TARDIS arrives outside. Doctor and Leela poke around.
On-board, a robot kills someone, and an obstruction is discovered. That obstruction is the TARDIS, which is moved out of the way with a crane.
The murder is discovered and the harvesting stopped. They’re on some sort of desert miner thingie. Chubb is dead. Someone killed him. They argue over who killed him while robots collect Doctor and Leela.
The robots are now in charge of the ship.
Doctor and Leela, interrogated by robots, break free to find the TARDIS and explore a bit. Robots sent to find the intruders. Doctor finds the TARDIS, Leela finds Chub. Doctor looks for Leela, finds another body and is closed into a separator, buried. Credits roll.
More murders, more blame, nobody will blame the robots. Ship sabatoged to blow up, and the Doctor is prevented from stopping it. Credits roll.
More Robot subjigation, and plans to kill the remaining humans. Doctor is being strangled. Credits roll.
Chasing around by robots. A human is behind it all to make the robots supreme. A robot makes the ultimate sacrifice to stop them, and the Doctor uses a cannister of helium to change the rebel human’s voice to it is not recognized by the robots and killed by one of them.
Doctor and Leela flee before help arrives.