Picking up a distress call from the edge of the known universe, the Doctor and Sarah Jane find themselves on Zeta Minor where a geological team has run afoul of some strange goings on...
| Actor | Role |
|---|---|
 Tom BakerThe Doctor | The Doctor |
 Elisabeth SladenSarah Jane Smith | Sarah Jane Smith |
 Frederick JaegerSorenson | Sorenson |
 Ewen SolonVishinsky | Vishinsky |
 Prentis HancockSalamar | Salamar |
| GGraham WestonDe Haan | De Haan |
 Louis MahoneyPonti | Ponti |
 Michael WisherMorelli | Morelli |
| TTerence BrookBraun | Braun |
| TTony McEwanBaldwin | Baldwin |
| HHaydn WoodO'Hara | O'Hara |
| MMelvyn BedfordReig | Reig |