"Frontios buries its own dead", or so the saying goes. The Doctor, Turlough and Tegan are forced into landing on the remote planet of Frontios, a human colony where deaths go unaccounted for. What lies beneath the surface, dragging its victims down?
| Actor | Role |
|---|---|
 Peter DavisonThe Doctor | The Doctor |
 Janet FieldingTegan Jovanka | Tegan Jovanka |
 Mark StricksonVislor Turlough | Vislor Turlough |
 Jeff RawlePlantagenet | Plantagenet |
 Peter GilmoreBrazen | Brazen |
 Lesley DunlopNorna | Norna |
 William LucasRange | Range |
 Maurice O'ConnellCockerill | Cockerill |
| RRaymond MurtaghRetrograde | Retrograde |
| RRichard AshleyOrderly | Orderly |
 Alison SkilbeckDeputy | Deputy |
| JJohn GillettThe Gravis | The Gravis |
| WWilliam BowenTractator | Tractator |
| GGeorge CampbellTractator | Tractator |
| HHeidi KhursandiTractator | Tractator |
| MMichael MalcolmTractator | Tractator |
| SStephen SpeedTractator | Tractator |