The only surviving fragment of the story is the third of four episodes. The Doctor, Vicki, and Steven arrive on a creepy silent planet and encounter small robots like three domes stacked on top of each other. They call them Chumblies. The travellers are attacked by blonde cloned female warriors from the planet Drahva in Galaxy Four. The Drahvians are at war with the Rills, the reptilian masters of the Chumblies. Both races have crash-landed on the planet, which will soon be destroyed, though The Doctor discovers it will explode sooner than they think.
The Drahvian ship is irreparable and their brutal leader Maaga (Stephanie Bidmead) wants to capture the Rill ship. She holds Steven hostage and sends The Doctor and Vicki to seize control of the vessel. The Rills are huge and impressive, look a bit like Warthogs, and breathe ammonia. But they are intelligent, telepathic, and less warlike than the Drahvians. In fact, they have offered to rescue the Drahvians but Maaga has refused.
The Doctor and Vicki return to the Drahvian ship to find Steven unconscious after Maaga tried to kill him in an airlock. Returning to the Rills, The Doctor uses a TARDIS power converter to charge the Rill ship. Maaga and her troops assault the craft but the Chumblies die defending it, except one who helps the TARDIS crew to escape as well. The Drahvians get what they deserve.
Intro
Part 1
Part 2
Part 3
Part 4