The planet Karfel is an oppressed world ruled over by a cruel tyrant - the Borad. Anyone opposing his will is cast out through a time tunnel known as the Timelash.

When the Doctor arrives he is asked to rescue a woman, Vena, who has been sent through the Timelash to Earth with a precious amulet the Borad needs returned. If the Doctor refuses, the life of his companion, Peri, is forfeit.

What is the truth behind the terrible power of the Borad? Why is he desperate for all-out war with the neighboring planet of Bandril? The Doctor falls in with the rebels, but to defeat the Borad means a one-to-one confrontation in the mad scientist's inner sanctum - and unless he acts quickly, Peri may undergo a terrifying change...