Doctor Who (1963) Season 8 Episode 7 The Mind of Evil (3)

The Doctor and Jo Grant are summoned to Stangmoor Prison by the Brigadier, who needs their assistance with a mysterious machine that has been causing violent tendencies in its subjects. The machine, known as the Keller Machine, is being used to rehabilitate dangerous criminals, but has had unexpected and disastrous results.

As the Doctor and Jo investigate, they find that something more sinister is at play. A terrorist organization known as the Mastermind has infiltrated Stangmoor Prison and is using the Keller Machine for their own nefarious purposes. The Doctor must not only stop the Mastermind's plans, but also uncover the true nature of the Keller Machine and its relationship to an alien race called the Mind Parasites.

As tensions rise and the situation becomes increasingly dire, the Doctor and Jo team up with the prison's inmates to thwart the Mastermind's plans and stop the Keller Machine from causing any more harm. But as the Doctor delves deeper into the mystery, he begins to realize that the true villain may not be who he thought it was, and that the Machiavellian scheme at play may be even more sinister than he could have imagined.

With pulse-pounding action, thrilling drama, and top-notch performances from the cast, "The Mind of Evil" is a standout episode in Doctor Who's ninth season that is sure to keep audiences on the edge of their seats.