The TARDIS has brought the travellers to the planet Skaro where they meet two indigenous races — the Daleks, malicious mutant creatures encased in armoured travel machines, and the Thals, beautiful humanoids with pacifist principles. They convince the Thals of the need to fight for their own survival.

Joining forces with them and braving Skaro's many dangers, they launch a two-pronged attack on the Dalek city. The Daleks are all killed when, during the course of the fighting, their power supply is cut off.