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 discover a stone spaceship underneath Warmsley's archaeological dig while Mordred summons Morgaine to Earth's dimension.

The Brigadier rescues the Doctor from the stone spaceship before they set out to locate Morgaine before she gains Excalibur.

Morgaine forces Ace and Shou Yuing to hand over Excalibur by threatening to release the Destroyer, so the Doctor and the Brigadier enter a dimensional portal to stop her.

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.

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.

England, the 1940s. The TARDIS brings the Doctor and Ace to a secret naval base during WWII. There, the time-travellers battle vampiric Haemovores and an ancient Viking curse!

The Doctor and Ace manage to convince Sorin to release them while Millington and Judson attempt to translate the Viking runes.

The Doctor and his friends come under attack from the Haemavores, allowing Millington to retrieve the flask containing Fenric's essence.

Fenric is loose and planning to use the Ancient Haemovore to poison the Earth with chemicals, unless the Doctor can defeat him in their centuries old game.

Perivale, England, the late 1980s. People are vanishing into thin air under the baleful stare of a very strange cat. The Doctor and Ace learn that, in the battle for survival, success can carry a terrible price...

The Doctor and Paterson manage to escape from the Master and join up with Ace and her friends, where the Doctor tries to find a way to get them all off the planet before it explodes.

Ace manages to transport the Doctor and the others back to Perivale but the Master is also there, preparing for a final showdown with the Doctor.