The original TV soundtrack, with new linking narration by a member of the cast, this 6-part adventure from 1971 stars Jon Pertwee as the Doctor with Katy Manning as his companion Jo Grant.

The Doctor is caught up in events at Stangmoor Prison, where Professor Keller's new machine is said to be able to remove all evil impulses from the minds of the prisoners. Nicholas Courtney and Roger Delgado also star as the Brigadier and the Master.