When the Doctor sets out to educate Charley on the darker side of her race's future, he does not anticipate being embroiled in the protracted Orion War. The front line may be light years away, but the human race's struggle for victory has led to desperate measures.

Trapped aboard a mysterious star destroyer in the Garazone System, the Doctor and Charley find themselves cast as scapegoats. But the real danger has yet to awaken...

The Cybermen have received the signal for reactivation.