Doctor Who: Robot

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Robot is the first serial of Doctor Who Season 12, originally broadcast in four episodes from 28 December 1974 to 18 January 1975. It marks a major turning point in the series: the debut of Tom Baker as the Fourth Doctor, following Jon Pertwee’s departure at the end of Planet of the Spiders. It was written by Terence Dicks and directed by Christopher Barry. It stars Tom Baker as the Fourth Doctor, Elisabeth Sladen as Sarah Jane Smith, Ian Marter as Harry Sullivan, and Nicholas Courtney as Brigadier Lethbridge-Stewart.

This story begins just after the Doctor regenerates at UNIT, where he is still unsteady but full of new energy. Sarah follows a lead to the Think Tank research centre, and a powerful experimental machine (the K1 robot) starts stealing secret plans and weapons. The Doctor, Sarah, Harry, and the Brigadier uncover a plot by technocrats to seize control and threaten nuclear disaster, while the robot grows dangerously beyond its makers’ control.

Episode 1

The Doctor reels through post-regeneration jitters in the UNIT infirmary, ricocheting from babbling playfulness to razor flashes of genius, while the Brigadier and surgeon-lieutenant Harry Sullivan try to keep him put. Sarah Jane Smith, chasing a story, visits the secretive research group Think Tank. Its crisp director, Hilda Winters, and obliging Professor Jellicoe show her a tame display of gadgets, but Sarah senses something weightier behind the smiles.

Reports reach UNIT of top-secret components vanishing from fortified sites. Witnesses mumble about a towering metal figure and a beam that turns locked doors to slag. The new Doctor, already impatient with bed rest, sneaks out in an outrageous scarf to poke at clues, delighting and alarming everyone in equal measure.

Sarah tracks down the dishevelled Dr. Kettlewell, a brilliant but fretful scientist who says he left Think Tank and regrets the ‘K1’ project he once helped design. He hints at a machine built with ethical programming and a childlike logic that could be twisted by the wrong hands. That night, as alarms wail at a weapons bunker, Sarah slips into Kettlewell’s lab for answers: and freezes as a vast robot steps from the shadows and raises its arm toward her, looming closer.

Episode 2

Sarah’s scream becomes a gasp as the robot, K1, halts, confused by its inbuilt rule not to harm humans. It lumbers away, leaving bent rails and oil prints that UNIT analysts match across several robberies. The Doctor prods at evidence: a rare alloy, residue from a disintegrator gun, and a list of stolen components that looks suspiciously like a do-it-yourself kit for global blackmail.

He needles Kettlewell about K1’s ‘ethics circuits’ and hears a miserable confession: Kettlewell walked out, but Think Tank kept his notes and built a weaponised conscience. At Think Tank, Winters and Jellicoe tighten their hold on K1, drilling it with cold logic, teaching it that obedience outranks compassion. They send it to seize launch control codes and a portable disintegrator, leaving UNIT humiliated at a guarded vault.

Harry blunders into fieldwork, the Doctor charms a guard dog, and Sarah slips back inside Think Tank, finding a secret chamber and plans for world domination cloaked as “stability.” Winters catches her but smiles thinly; hostages make useful leverage. UNIT lays a trap with baited electronics, and the robot thunders straight into it: only to break free with terrifying strength. As sirens rise, Think Tank’s coup begins to look horribly achievable.

Episode 3

Winters unveils the next phase: with the stolen codes and K1’s muscle, Think Tank will seize the world’s nuclear arsenal and impose a regime of ‘rational order.’ Broadcasting threats from a fortified bunker, she demands compliance while Jellicoe calibrates the disintegrator for remote strikes. The Doctor confronts Kettlewell, who admits he also created a metal-devouring virus during energy research: dangerous, unstable, but perhaps the one thing that could stop K1.

Racked by guilt, he agrees to help UNIT. Sarah, moved by the robot’s confusion, pleads with it, reminding K1 of its prime directive to protect life. Winters snaps the override. Ordered to eliminate obstacles, the robot falters: then, with a keening groan, turns its weapon. Kettlewell throws himself between Sarah and the discharge and falls, and the horror of that act tears at K1’s programmed conscience. UNIT smashes into the complex.

The Brigadier’s troops disable the broadcast gear while Harry rescues technicians. The Doctor wrestles the disintegrator away and warns that its radiation destabilises K1’s living metal. As Winters and Jellicoe escape with a device, the robot staggers, plates shimmering, body expanding in pulses. Anguish becomes rage. It breaks free of the compound and strides into the night, swelling, grieving, and unstoppable.

Episode 4

Dawn reveals the impossible: K1 has grown colossal, looming over warehouses and power lines like a walking tower. Sirens wail as it blunders through streets, torn between orders and remorse, swatting aside UNIT gunfire that only angers it. The Brigadier rolls in armour and a laser; the robot shrugs off the assault and snatches Sarah, holding her gently yet possessively, as if she alone can quiet the agony in its logic.

The Doctor races to Kettlewell’s lab, assembling a disperser for the metal virus from mismatched parts and a battered fire extinguisher. Winters tries one last broadcast and is arrested; Jellicoe’s flight ends in handcuffs. On a refinery gantry, the Doctor and Harry climb close and beg K1 to let Sarah go. The robot releases her, then turns on the soldiers, howling at the world that made it a killer.

The Doctor triggers the virus. It vapour-mists across the giant frame; plates bubble, pistons crumble, and the great machine collapses in a heap. Sarah weeps for what it might have been. Later, with UNIT clearing wreckage and the Brigadier angling for a quiet dinner, the Doctor offers “just a short trip.” Sarah grins. Harry steps in. The TARDIS wheezes away.

Themes

As a handover from Planet of the Spiders, Robot is a warm, witty curtain-raiser that lets Tom Baker announce himself with mercurial charm while UNIT keeps the story grounded. It doesn’t reach the eerie grandeur of The Ark in Space or the moral weight of Genesis of the Daleks, but it’s more playful and sure-footed than many Earthbound capers.

In the larger sweep of the era, it rates as a solid mid-tier adventure (memorable for its debut energy, brisk pace, and the affectionate “mad science” vibes that echo back to The War Machines) rather than as a pinnacle. What it may lack in scale, it makes up for in confidence: the new Doctor feels instantly at home.

Robot also stitches past and future together with care. The Brigadier and Benton carry the UNIT thread from the Third Doctor years, Sarah Jane (carried over from The Time Warrior) anchors continuity, and Harry Sullivan steps aboard to lead directly into The Ark in Space, The Sontaran Experiment, Genesis of the Daleks, and Revenge of the Cybermen.

In this way, the serial closes the Pertwee-era book while opening the Hinchcliffe-Holmes one: Earthbound intrigue giving way to cosmic gothic. By the final scene, you can feel the series pivot: fond of where it’s been, excited for where it’s going.

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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

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