"This is High Treason, and for this you deserve death. However, in view of your past service, the sentence is commuted to exile. You leave Gallifrey this day, never to return."

A chain of events has been set in motion that will change the Doctor and Peri forever. A chain that involves old enemies as well as old friends.

How does Peri come to be the leader of a gang of rebel fighters on an outlying planet? Who is the mysterious "General" against whom they are rebelling so violently? Where does the so-called "Supremo", leader of the Alliance forces ranged against the General, come from, and why is he so interested in Peri?

The answers lie in the origins of a conflict that will affect the whole cosmos — a conflict that will find humans, Sontarans, Draconians and even Cybermen fighting together for the greater good and glory. For the Supremo.

It is a conflict that will test both the Doctor and Peri to the limit, and bring them face to face with the dark sides of their own personalities.