The Doctor and Charley set off to the Garazone System bazaar, but instead discover a deadly enemy on a derelict star destroyer.

To prove that he and Charley are innocent of murder and get the TARDIS back, the Doctor must face the deadly Cybermen.

The Cybermen are on the advance, but the Doctor has a plan. Meanwhile, someone aboard the Vanguard has a sinister agenda.

With an ion storm threatening to strike at any moment, the Doctor faces a race against time to defeat the Cybermen.