In the far future, the city of Hope isn't a place for the weak.

The air is thick with fog. The sea burns. Law and order are a thing of the past. Headless corpses are being found at the edge of the city, and the militia can't find the killer. Members of a deranged cult mutilate themselves while plotting the deaths of their enemies.

Even the Doctor can't see any possibility of redemption for this cursed place. All he wants to do is leave, but to do so he needs the TARDIS — and the TARDIS is lost in the depths of a toxic sea. When the most powerful man on the planet offers to retrieve the TARDIS — for a price — the Doctor has no choice but to accept.

But while the Doctor is hunting a killer, another offer is being made — one which could tear the Doctor and his companions apart...