As UNIT are transporting a nuclear warhead around Carbury, knights in armour arrive to continue waging a war that began thousands of years ago, but in a wholly different dimension.
The Doctor and Ace explore King Arthur's spaceship deep under Lake Vortigern, while Brigadier Lethbridge-Stewart arrives in Carbury where he encounters Morgaine.
Furious at her inability to find and engage Arthur in battle, Morgaine threatens to unleash the Destroyer upon the planet unless the Doctor gives her what she wants.
The Brigadier slays the Destroyer while Morgaine takes control of UNIT's nuclear warhead and prepares to start a countdown that will destroy Earth forever.
The Doctor and Ace explore Victorian house Gabriel Chase and realise it hides just as many dark secrets in its drawing room as it does in its dark cellar.
The Doctor and Scotland Yard's finest, Inspector Mackenzie, attempt to question Josiah Smith while both Light and Control emerge from their respective slumbers.
Only Redvers, still searching for the elusive Saxe-Coburg, seems able to withstand Light and communicate with Control. Ace realises her past actions need to be dealt with
As Russian forces approach the English coastline, an ancient evil stirs beneath the surface of the water. For Ace and the Doctor, a deadly game of revenge has begun.
The Viking runes in the crypt contain a secret to Ace's past. Meanwhile, Millington and Judson's Ultima machine offer to break the chains of the Wolves of Fenric.
The Haemovores attack St Jude's church.
The Ancient Haemovore stands upon Earth once again, determined to change the future by erasing the past. Ace finally feels love for her mother.
Trying to work out why people have been disappearing from Perivale, Ace is cornered by Kara, a Cheetah-Person who transports her to a far-off planet..
The Doctor and a number of people from Perivale follow Ace to the Cheetah-People's world, where the Master lies in wait. He cannot leave without the Doctor's assistance.
As the alien world dies around them, the Doctor and the Master fight like animals before escaping to Earth, where their war ends. And somewhere else, the tea is getting cold.