The Doctor, Romana, Adric and K9 encounter the enslaved time-sensitive Tharils, who lead them to a white void occupied only by the ruins of an old building and a spaceship - a dimension that might be the key to escaping E-Space.
| Actor | Role |
|---|---|
 Tom BakerThe Doctor | The Doctor |
 Lalla WardRomana | Romana |
 Matthew WaterhouseAdric | Adric |
 John LeesonK9 (voice) | K9 (voice) |
 Clifford RoseRorvik | Rorvik |
 Kenneth CopePackard | Packard |
| DDavid KincaidLane | Lane |
| FFreddie EarlleAldo | Aldo |
| HHarry WatersRoyce | Royce |
 David WestonBiroc | Biroc |
| VVincent PickeringSagan | Sagan |
| RRobert VowlesGundan | Gundan |
 Jeremy GittinsLazlo | Lazlo |