S8E8
Tense, high-stakes, with moments of dark triumph and lingering unease
Written by Don Houghton
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The Mind of Evil Part 4

When the Master uses an alien mind parasite to amplify evil in a prison, the Doctor must overcome the machine's influence, stop the Master from weaponizing a deadly gas missile, and save humanity from succumbing to ultimate malevolence.

In "The Mind of Evil - Episode Four," the Master continues his sinister scheme, using the Keller Machine and its alien mind parasite to amplify evil within Stangmoor Prison. The Doctor, weakened but defiant, resists the machine's influence while grappling with the knowledge of its deadly nature. The Master, seeking to exploit the chaos, forces the Doctor to cooperate by threatening Jo Grant's life. Meanwhile, an attempted prison transfer reveals Vosper's complicity in the Master's plans.

The Master's control over the alien parasite falters as it grows stronger, leading to a confrontation within the process theatre. The Doctor, though still recovering, joins forces with Jo and Doctor Summers to help recover from the machine's effects. The Master, undeterred, plots to steal Thunderbolt, a British gas missile, aiming to weaponize it against a peace conference in London. He enlists Mailer and a group of convicts to hijack the missile convoy, promising them freedom and riches.

Jo and the Doctor escape their cell, discovering the Master's plan through confiscated documents. They realize the urgency of stopping him before he can unleash the Thunderbolt. The Brigadier and UNIT become involved after Captain Yates' convoy is ambushed. Yates manages to follow the stolen missile to an airfield but is captured. Benton provides crucial information that leads the Brigadier to suspect Stangmoor Prison's involvement.

As the Master prepares to launch the missile, the Doctor and Jo race against time to thwart his plans. They realize the alien creature from the Keller machine can move and cause death wherever it goes, heightening the stakes and creating uncertainty for everyone involved. The confrontation escalates as UNIT closes in, the Doctor faces the Master, and the fate of the peace conference and potentially the world hangs in the balance. The story culminates in a final showdown, where the Doctor must destroy the alien entity and prevent the Master from unleashing his destructive scheme.


Events in This Episode

The narrative beats that drive the story

31
Act 1

The Master struggles against the Keller Machine's influence, then revives the Doctor, who had nearly died from the ordeal. The Master reveals his awareness of the Doctor's two hearts and forces the Doctor's cooperation by threatening Jo Grant's life. Meanwhile, Vosper transfers Doctor Summers from the cell, confirming Jo's specific importance to the Master's plan to use her with the machine. The Doctor warns the Master about the alien mind parasite within the machine, which feeds on evil and will eventually consume the Master. The Master dismisses the warning but later battles the machine, losing control as it confronts him with his greatest fear—the Doctor's laughter. He flees the Process Theatre, barring the door to starve the creature. Doctor Summers, briefly allowed to examine the Doctor, expresses amazement at his non-human physiology and the severity of his mental and physical trauma, suggesting the Doctor is in a coma. The Doctor, however, soon recovers consciousness, feigning weakness to gain an advantage.

Act 2

Exhausted from his confrontation with the machine, the Master reveals his true objective to Mailer: hijack the British Thunderbolt gas missile, which the government plans to dump at sea. He promises Mailer and the convicts freedom, unlimited money, and passage anywhere in the world in exchange for their participation. The Master intends to weaponize the missile against a peace conference in London. Jo and the Doctor, having recovered, stage a quick, decisive escape from their cell, with the Doctor displaying unexpected physical prowess. They make their way to the Governor's office, where they discover the Master's plan through a slide projector showing the Thunderbolt missile. Simultaneously, Mailer and the convicts ambush the missile convoy, killing the escort and hijacking the Thunderbolt. Captain Yates, though injured, manages to follow the stolen missile to an airfield, where he is captured by the convicts and military personnel assisting the Master.

Act 3

UNIT begins its investigation into the ambush, with the Brigadier leading the operation. Benton, having survived the attack, provides a crucial detail about seeing a 'Black Maria' police van, which leads the Brigadier to suspect Stangmoor Prison's involvement. Back at the prison, the Doctor and Jo debate their next move. Jo suggests escaping, but the Doctor insists on staying to confront the alien creature from the Keller Machine, identifying it as a deadly mind parasite. He rejects Jo's offer of a gun, stating his preference for non-violent solutions. The Master departs Stangmoor in his car, signaling a shift in his operations. As the Doctor and Jo prepare to enter the Process Theatre, the Keller Machine, and the creature within it, vanish. The creature then reappears in the cell block, killing Charlie, confirming its ability to move freely and lethally throughout the prison. This revelation elevates the threat, forcing the Doctor to adapt his strategy from confronting a static machine to tracking a mobile, deadly entity.