Doctor Who: The Sontaran Experiment

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The Sontaran Experiment is the third serial of Season 12 of Doctor Who, first broadcast in two episodes on BBC1 on 22 February and 1 March 1975. It was written by Bob Baker and Dave Martin and directed by Rodney Bennett. It stars Tom Baker as the Fourth Doctor, Elisabeth Sladen as Sarah Jane Smith, Ian Marter as Harry Sullivan, and Kevin Lindsay as the Sontaran officer Styre.

The Doctor, Sarah, and Harry transmat from Nerva to a bleak, deserted Earth and find a small group of human surveyors being hunted and tested by Styre. As Sarah and Harry try to help the frightened survivors, the Doctor challenges the Sontaran’s cruel experiments and uncovers a plan to assess humanity’s weaknesses for invasion. With quick thinking and courage, the trio turn the tables on Styre, and the Doctor proves that Earth still has defenders: even in its silent future.

Episode 1

Fresh from Nerva Beacon, the Doctor, Sarah, and Harry transmat to a bleak, wind-scoured Earth in the far future. The land is empty, the cities long gone, and something metallic prowls the rocks. They split up to survey the area; Sarah is seized by a bulbous service robot and carried away, while Harry tumbles into a deep pit lined with jagged metal.

The Doctor deduces they are on Earth by testing gravity and finds scuffed footprints and a smashed transmitter. A ragged man, Roth, bursts from hiding and babbles about an alien torturer and missing crewmates. He belongs to a small GalSec survey team that has crash-landed and begun to vanish. The Doctor frees Harry and follows the robot’s tracks to a crude experimental ground: wires, restraints, and instruments for measuring pain, fear, dehydration, and endurance.

Elsewhere, GalSec survivors (led by wary Krans and the uneasy Vural) capture the Doctor at gunpoint, convinced he is a rival colonist. Roth tries to warn them and is silenced by a sniper beam. In a rocky hollow, Sarah wakes strapped beneath a device that stabs at her nerves with manufactured terror. A squat, leathery figure steps from a half-buried sphere: Field Major Styre of the Sontaran G3 Military.

Episode 2

Styre continues his cold “survey,” timing human reactions while his robot hunts the stragglers. The Doctor bargains to buy minutes and studies the Sontaran’s equipment and imperatives. He learns Vural has been compromised (wired with a control implant and coerced into luring victims) yet even Vural’s betrayal comes from desperation to save his crew.

Sarah slips free and sabotages the robot with a boulder and Harry’s quick thinking, giving the prisoners a chance to scatter. Styre, eager to complete his report and clear the way for invasion, challenges the Doctor to single combat. The Doctor turns terrain and stamina against him, harrying the armoured warrior, feinting toward the probic vent weakness in the back of his neck. Vural lunges to help and is blasted down.

While Sarah rallies the GalSec men, the Doctor slips to Styre’s ship and rewires the power feed. Drained and furious, Styre retreats to recharge; the sabotaged system backfires, sucking his life support dry and collapsing him in his armour. Over the communicator, a Sontaran Marshal orders status; the Doctor bluffs, and with Styre dead and his experiments void, the assault is aborted. The Doctor repairs the transmat link. Bidding the shaken GalSec survivors hope, the trio shimmer back to Nerva.

Themes

As a taut, two-part interlude, The Sontaran Experiment proves how sharp Doctor Who can be when it strips the story to steel and bone. The all-location bleakness and Tom Baker’s flinty authority give it bite, even if it doesn’t reach the mythic stature of Genesis of the Daleks or the lyrical menace of The Ark in Space.

It lands as a confident mid-tier outing. It is leaner and nastier than many Earthset tales, and more cohesive than some longer curios. Its clinical cruelty and survival tests foreshadowing the gothic science to come. What it lacks in scale, it repays in focus, tension, and a villain whose methods feel chillingly procedural.

As a hinge in the season’s mini-arc, it links past and future with precision. The Sontarans’ return recalls their debut in The Time Warrior, while the Nerva transmat carries the thread forward from The Ark in Space. The Doctor, Sarah Jane, and Harry conclude their trial on a ravaged Earth only to be wrenched away by the Time Lords into Genesis of the Daleks, and the time ring will ultimately loop them back to Nerva in Revenge of the Cybermen.

Even beyond this run, the legacy echoes through later returns like The Invasion of Time and The Two Doctors. By the close, The Sontaran Experiment has done its job perfectly: a brutal, efficient bridge that keeps the era’s momentum surging.

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This is a chapter from Craig Hill’s book “Doctor Who – The Fourth Doctor”, chronicling every episode featuring the Fourth Doctor. It is available on Amazon.

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To view the list of other Doctor Who serials, please click this link

Doctor Who Episode Guides for Sale on Amazon

Step aboard the TARDIS and journey across the universe with every incarnation of The Doctor in this series of unofficial Doctor Who episode companions.

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