Doctor Who: The Krotons

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The Krotons is the fourth serial of Season 6 of the classic Doctor Who series. Originally broadcast in four episodes from 28 December 1968 to 18 January 1969. It was written by Robert Holmes and directed by David Maloney. It stars Patrick Troughton as the Doctor, Frazer Hines as Jamie McCrimmon, Wendy Padbury as Zoe Heriot, and Philip Madoc as Eelek.

Robert Holmes makes his Doctor Who debut (he would later become one of the show’s most celebrated writers), the story was originally penned years earlier and reworked by script editor Terrance Dicks.

The TARDIS lands on a distant world where the Gond people live under the cold rule of the Krotons, crystal-bodied beings who take the brightest students away in a false “honour.” Zoe’s brilliance draws her into their tests, the Doctor follows to protect her, and Jamie rallies the Gonds as unrest grows. Although made quickly and on a modest budget, The Krotons features sharp satire on education, social conformity, and authoritarian control.

Episode 1

The TARDIS lands on a sun-blasted plain where a stone city sits under the watch of a hulking crystal machine the Gonds call the Dynatrope. The Doctor, Jamie, and Zoe arrive as a “Selection” ceremony names two top students (Abu and Vana) to enter the machine as an honour. Thara, the leader’s hot-blooded son, rails that the chosen never return.

Moments later, Abu steps through a door of light and is instantly dispersed to powder; Vana staggers back, traumatised, whispering about metal voices. Selris, the mild Gond leader, pleads for calm, while the ambitious councillor Eelek urges obedience to their “Benefactors,” the Krotons, who taught the Gonds using mind-tests in the Learning Hall. The Doctor inspects the teaching machines and hears hidden commands in their hum.

Zoe, unable to resist a challenge, sits the test and scores off the scale. To protect her, the Doctor sits too. The Dynatrope immediately summons the two “High Brains.” Thara smashes at the doors, but the machine’s crystal jets drive him back. Jamie swears to get them out. Inside, the Doctor and Zoe step into a chamber of shimmering facets where a honeyed voice praises their intellect and promises partnership. The air prickles. Somewhere beneath the floor, something wakes.

Episode 2

The chamber tests them with logic problems blooming across panels, a needle-spray that burns like acid, a platform that tilts toward a crystal vat. Meanwhile, a pulse drinks in their mental energy. The Doctor stalls with wrong answers, then flips a sequence and ejects them through a side door. Their effort has done something worse: the Dynatrope begins to grow a Kroton, a crystal lifeform knitting itself together from suspended slurry, drawn by the “High Brains.”

Jamie, searching for his friends, slips inside and is seized by a snaking metal arm. A half-formed Kroton studies him, declares him “low-brain,” and orders the Gonds to deliver the Doctor and Zoe or suffer dispersal. Outside, Eelek grabs the moment to challenge Selris’s authority, urging an axe-and-fire assault. The Doctor gathers residue from the chamber and watches it fizz and flake when a drop of acid touches it.

He befriends Beta, a nervous Gond chemist, and starts listing reagents; perhaps the Krotons’ crystalline matrix can be dissolved. Vana, still in shock, mutters about the machine “drinking thoughts.” The newly completed Kroton stomps into the square, faceted head glittering, and announces that the era of teaching is over. The Gonds will obey, or be erased. Its partner begins to form in the vat.

Episode 3

Two Krotons now stand at the Dynatrope’s gate, weapons hissing, demanding the surrender of the High Brains. Jamie, locked in a cell, baits a guard and slips out, linking up with Thara to protect Zoe while the Doctor and Beta work. Eelek uses the crisis to seize command from Selris and orders an attack; axes bounce off crystal hides and a dispersal ray kills without a mark.

The Krotons retaliate by smashing the Learning Hall: no more “education,” only harvest. The Doctor refines his insight: the Krotons are crystalline organisms held in a chemical suspension, reconstituted by directed thought energy; their lattice collapses in strong acid. He and Beta raid the stores for the right mix, narrowly avoiding Eelek’s spies. Inside the Dynatrope, the Krotons reveal their plan.

Their ship crashed here years ago; to leave, they need continuous feeds of high-grade mental energy to pilot through space. They strap Zoe and the Doctor into headframes to drain them completely and order the Gonds to supply more “bright minds” as fuel. Jamie and Thara force a hatch and drag Zoe free, but the Doctor stays to watch gauges and count pipes. Somewhere in the tank system there must be a way to pour ruin into a Kroton’s veins.

Episode 4

With Eelek grandstanding in the square and the Krotons forcing a launch countdown, the Doctor and Beta complete a batch of concentrated acid (“sulphuric,” the Doctor grins) hot enough to eat a beaker. Thara and Jamie stage a diversion at the Dynatrope door while Selris, reclaiming a shred of authority, slips the Doctor a master key. Inside, crystal conduits throb; a control pillar rises; the Krotons herd the Gonds toward the vats to “test” for more High Brains.

The Doctor darts through piping to the feed reservoir and starts uncapping valves. Outside, Eelek’s bluster collapses as another dispersal blast drops a would-be hero. Beta and Zoe haul the acid canisters to the hatch. A Kroton looms; Jamie and Thara drag it off balance and jam its gun. The Doctor tips the first load into the Dynatrope’s heart.

A harsh screech answers as the fluid turns milky; faces craze and slump. The Krotons stagger, their lattice softening; the ship’s column buckles. One lurches for the exit; Selris blocks the way and is cut down holding the door. The last canister goes in. The Dynatrope sags like melting ice and collapses in a hissing heap. Morning finds Eelek chastened, Beta and Thara planning schools without masters, and Vana finally smiling. The travellers slip back to the TARDIS as crystal dust drifts on the air.

Themes

As a change of pace after the sleek modernism of The Invasion, The Krotons lands mid-table for Season 6. It is more coherent and lively than The Dominators, though a clear step below the audacity of The Mind Robber and the grandeur of The War Games.

Its strengths are the Doctor–Jamie–Zoe trio in perfect sync and the way Zoe’s intellect drives the plot, giving the story a crisp, puzzle-box momentum. As Robert Holmes’s first contribution, it doesn’t reach the heights of his later triumphs, but you can feel the wit and structural snap that will blossom in classics like The Talons of Weng-Chiang and The Caves of Androzani.

In the tapestry of the run, it follows The Invasion and points straight to The Seeds of Death, with its test-and-control society echoing earlier themes from The Macra Terror and anticipating later critiques of technocracy in The Sun Makers.

The notion of “learning machines” posing as benefactors nods ahead to false-saviour tales such as The Face of Evil, while Zoe’s analytical courage previews the moral problem-solving that culminates in The War Games. Modest in scope but smart in execution, The Krotons acts as a connective hinge, consolidating a sharp team dynamic while sketching concerns the series will keep worrying at for years.

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This is a chapter from Craig Hill’s book “Doctor Who – The Second Doctor”, chronicling every episode featuring the Second 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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