Publisher's Synopsis
A dangerous adventure begins for the Doctor and Jo Grant when they visit Stangmoor Prison for a demonstration of the new Keller Machine. The device is said to extract negative emotions from convicted prisoners, leaving them pacified and reformed. But when it apparently goes wrong, a far more sinister purpose is revealed
The Doctor s old enemy, the Master, is behind the machine, working in conjunction with an alien mind parasite. As unrest builds amongst Stangmoor s prisoners, the Master takes control, his ultimate aim to hijack a deadly missile and threaten the World Peace Conference taking place in London. As Brigadier Lethbridge-Stewart leads UNIT in the defense of both the missile and Stangmoor, the Doctor and Jo must fight to stay alive and help avert a third world war! "
