The Doctor and Jo visit Stangmoor prison to view the Keller machine, a revolutionary new treatment for the criminal mind. The Doctor senses something is amiss and his instincts are soon proved correct.
Newly recovered, the Doctor escapes from his cell with Jo. The Master plans to use the Keller Machine to recruit the rioting inmates at Stangmoor Prison and attack the World Peace Conference.
S1E3 24 min