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?
The Doctor brings Ace to Gabriel Chase, an old house that she once burnt down in her home town of Perivale. The year is 1883 and the house is presided over by Josiah Samuel Smith, who turns out to be the evolved form of an alien brought to Earth in a stone spaceship that is now in the basement…
The TARDIS materialises at a secret naval base off the coast of Northumberland toward the end of the Second World War. Dr Judson, a scientist there, has created the Ultima Machine, an early computer designed to break German codes. The base’s Commander Millington plans to let a Russian commando unit led by Captain Sorin steal the Machine’s core, which he has booby-trapped with deadly toxin…
Something savage is stalking the streets of London, and humans are its prey. People are vanishing. But only young, healthy people. When the Doctor takes Ace on a sentimental journey to her old neighbourhood, they discover all her friends are missing. The Doctor and Ace are drawn into investigating, and become prey themselves.