Despite protestations against being the Evil One, mounting evidence points to the Doctor's prior involvement with Leela's people, and an error in judgment he once made in their distant past that puts them all in immediate jeopardy.

As the Saveteem and Tesh finally close in for a fight to the death, the powerful but long-suffering Xoanon ignores their strife to commit its full resources toward killing the Doctor, even to the extent of destroying everyone.