The Doctor and Jo head out to Stangmoor Castle-turned-Prison to witness a demonstration of a new machine that’s said to remove the dark urges from violent offenders completely. The Doctor is suspicious of the blasted thing, especially when the inevitable mysterious deaths begin.
Meanwhile, the Brigadier is coordinating security for the World Peace conference when sensitive files from go missing from the Chinese delegation’s quarters.
Benton and Yates do their best to smuggle Britain’s outlawed Thunderbolt nerve-gas missle to be destroyed before the other nations realize they still have one.
And all the while, the Master is still on Earth, more dangerous than ever.