Sontaran Field Major Styre is conducting experiments on the survivors of future Earth in preparation of a full-scale Sontaran invasion of the planet. Can the Doctor defeat Styre and save the world?
| Actor | Role |
|---|---|
 Tom BakerThe Doctor | The Doctor |
 Elisabeth SladenSarah Jane Smith | Sarah Jane Smith |
 Ian MarterHarry Sullivan | Harry Sullivan |
| KKevin LindsayStyre / The Marshal | Styre / The Marshal |
 Donald DouglasVural | Vural |
| GGlyn JonesKrans | Krans |
| PPeter WalsheErak | Erak |
| PPeter RutherfordRoth | Roth |
 Terry WalshZake | Zake |
| BBrian EllisPrisoner | Prisoner |