The upcoming festive special will see the return of one of the Doctor's biggest and most feared enemies - the Daleks. The Doctor is locked away in a high-security alien prison. Isolated, alone, with no hope of escape. Far away, on Earth, her best friends, Yaz, Ryan and Graham have to pick up their lives without her. But it's not easy. Old habits die hard. Especially when they discover a disturbing plan forming. A plan which involves a Dalek.…