- Episodes: 4 Episodes
- Doctor: 7th Doctor
- Companions: Ace, Lethbridge-Stewart
- Aliens/Monsters: The S’rax, The Destroyer
- Setting: Earth
Doctor and Ace receive a mysterious distress signal and land in the Earth village of Carbury, where a nuclear convoy has halted. The Doctor’s concern is heightened when knights from another dimension begin to land in the area. Nearby is Lake Voortigen, the mythical resting-place of Excalibur, King Arthur’s mystical sword… But the lake holds a more sinister secret. A spaceship from the same alien dimension lurks under the lake – but does it really contain Arthur’s corpse? And what is it that the Witch Queen, Morgaine, is really after?