Berserker

Sunspire was devastated by the Daleks centuries ago. The last of its people are returning to seek out their heritage in an underground bunker, and save their species from extinction. Case and the War Doctor join the mission, posing as a Dalek-Killer and her squire.

But the bunker has an occupant: a single Berserker Dalek, driven insane by four hundred years of solitude...