Steven Taylor thought he'd left a life of adventure behind when he said goodbye to the Doctor and forged his future as the leader of a world. But decades later, when a broken and grieving Steven awakes aboard a mysterious spacecraft, terror is close at hand.

What is the purpose of the ship's voyage and why has it collected a random group from different points in time and space? What sinister presence lurks within the darkness that smothers its corridors? And can Steven really trust the new arrival claiming to be the Doctor...?