- Episodes: 4 Episodes
- Doctor: 5th Doctor
- Companions: Adric, Nyssa, Tegan
- Aliens/Monsters: N/A, The Master
- Setting: Earth, Castrovalva
Still weak and confused after his fourth regeneration, the Doctor retreats to Castrovalva to recuperate. But Castrovalva is not the haven of peace and tranquility the Doctor and his companions are seeking. Far from being able to rest quietly, the unsuspecting time travellers are once again caught up in the machinations of the Master. Only an act of supreme self-sacrifice will enable them to escape the maniacal lunacy of the renegade Time Lord.