Professor Emil Keller has created a machine that can pacify even the most dangerous of criminals. But when the Doctor and Jo arrive at Stangmoor Prison for a demonstration, things start to go horribly wrong - especially when they discover that the Doctor's old enemy the Master is responsible for the machine.
Released: Mar 06, 1971
Runtime: 150 minutes
Genre: Science Fiction, Drama, Adventure
Stars: Jon Pertwee, Katy Manning, Nicholas Courtney, Richard Franklin, John Levene, Roger Delgado
Crew: Don Houghton (Writer), Timothy Combe (Director), Barry Letts (Producer), Terrance Dicks (Script Editor), Dudley Simpson (Music), Roger Harvey (Editor)