While the Doctor, Ben and Polly find themselves joining in the shadowplay, it becomes clear that a real-life murderer is stalking the dark, disused corridors of the Galaxian. But worse than this: there's a sinister force waiting for events to unfold. A terrible secret is hidden on board the Galaxian, and if it is discovered, nothing - least of all murder - will ever be the same again. If this is a game, the stakes just got higher.