Doctor Who: The Power of Kroll

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The Power of Kroll is the fifth serial of Doctor Who Season 16 and part of the season-long Key to Time arc. It was broadcast in four episodes from December 23, 1978, to January 13, 1979. It was written by Robert Holmes and directed by Norman Stewart. It stars Tom Baker as the Fourth Doctor, Mary Tamm as Romana, Philip Madoc as Fenner, Neil McCarthy as Thawn, and John Abineri as Ranquin.

The Doctor and Romana arrive on the swamp moon of Delta Magna, where a methane refinery clashes with the native “Swampies,” who worship the giant creature Kroll. As fear and greed push the humans toward a brutal solution, Kroll awakens and rises from the marshes, threatening everyone. The Doctor works to stop a massacre, learn the truth behind Kroll’s power, and find the fifth segment of the Key to Time hidden in the most dangerous place. With calm courage and quick thinking, he ends the violence and leaves the moon a little safer than he found it.

Episode One

The tracer pulls the Doctor, Romana, and K9 to a sodden moon: endless reed marsh, methane mist, and a grim little methane-refinery on stilts. The human crew (Thawn, Fenner, Dugeen, and Harg) watch numbers and treat the native “Swampies” as a nuisance.

In the reeds, a smooth talker named Rohm-Dutt slips rifles to the Swampies, promising leverage against “dryfoot” colonists. The tracer hums, then goes oddly weak, as if what it seeks is everywhere and nowhere at once. Captured by Swampies and hauled before High Priest Ranquin, the travellers learn of Kroll, a god of the deep that wakes in times of crisis. The Doctor doubts myths but notes curious glyphs that look like cephalopods wrapped around a star.

Back at the refinery, Thawn snarls about sabotage and orders a sonic probe test that could kill anything in the marsh. Dugeen, decent and worried, says it’s illegal; Thawn smiles and does it anyway. In the temple, Ranquin declares the strangers a fitting sacrifice; Rohm-Dutt whispers that fireworks will force the dryfoots to retreat, and pockets his money. Out on a mudflat, the Doctor and Romana are bound to stakes as drums rise. Far out in the reed-sea, a bulge forms. A tentacle lifts, silt sheets off it, and something impossibly large turns toward the shore.

Episode Two

The tentacle strikes, swamping boats and dragging men under; Rohm-Dutt fires wildly and vanishes with a single, silencing splash. The Doctor cuts himself free and drags Romana into the reeds as Ranquin proclaims Kroll appeased and promises holy war. At the refinery, instruments scream: a life-form the size of a city is moving beneath the pipes.

Thawn orders a full sonic barrage to “discourage” it: Fenner calls it murder. The probe fires; out in the marsh, reeds flatten and the creature’s wake boils. Dugeen confronts Thawn with a theory: someone hired Rohm-Dutt to arm the Swampies as a pretext for a massacre and resettlement. Thawn shoots him dead, then calls it an accident. The Doctor and Romana trail Swampie hunters to a shrine and see a mural: a small squid swallowing a shining crystal and growing monstrous.

The tracer quivers toward the depths. The Doctor goes still: if a segment of the Key to Time went down a squid’s gullet long ago, Kroll could be the result. Sirens wail. The marsh heaves up in a wall of black water. Kroll’s vast head and ringed beak push the surface aside; its tentacles wrap a refinery leg and squeeze. Steel screams. The Doctor shouts for the pumps to cut out as the entire structure tilts.

Episode Three

With Kroll wrapped around the rig, Thawn arms the main sonic generator for a killing pulse that will pulp everything in a mile: the Swampies included. Fenner balks; the Doctor sabotages the firing circuit and pleads for a surgical fix. He needs to reach Kroll’s core and touch it with the tracer to collapse the segment’s field.

Romana maps a route through maintenance ducts; K9 computes stress points in the swaying structure. On the shore, Ranquin rallies warriors for a final assault; Varlick, a younger zealot, hesitates: Kroll’s hunger doesn’t spare believers. In a mud chapel the Doctor reads more carved history: settlers once worshipped the creature as a food-source spirit; only after the “shining gift” fell did faith turn to terror. The refinery groans. Harg is crushed in a buckling corridor; Fenner keeps consoles alive with gritted calm.

The Doctor reaches a pipe gallery over open water just as Kroll’s eye swells up beneath a grate like a rising moon. He inches the tracer through spraying valves and feels the field: it’s there, at the nucleus, buried under tons of alien flesh. On the temple platform Ranquin raises a knife over Romana, declaring the dryfoots consecrated. Kroll lifts again, blotting the horizon. The Doctor steadies his hand for one impossible touch.

Episode Four

Thawn storms the temple with guards, uses the “atrocity” as proof of Swampie savagery, and shoots Ranquin as the priest tries to stab the Doctor; Varlick hurls Thawn into the mud in fury. Back at the refinery, Kroll hauls itself higher, suckers locking on glass and steel. The Doctor and Romana scramble to the pump head furthest out over the marsh.

Beneath them, an eye the size of a house rolls and fixes on the tiny movement. The platform buckles; the Doctor swings down on a cable and, at full stretch above the pupil, drives the tracer home. Light flares along the tendons. A thunder runs through the body. Kroll convulses and collapses inward, vast flesh rippling as if a tide were going out inside it. When the glare clears, the tentacles are gone.

In the churned water below, small, ordinary squids tumble away into the reeds. In the cockpit, Fenner powers down the sonics and breathes. On shore, Varlick lowers his spear and talks (really talks) to a shaken refinery crew about boundaries and the marsh. The Doctor clicks the transformed segment into its niche and pockets the now-quiet tracer. He tells Romana that sometimes gods are made by accidents, and unmade the same way. The TARDIS fades over flat water, leaving ripples and the smell of salt.

Themes

As the mud-slick fifth leg of the Key to Time quest, The Power of Kroll trades the elegance of The Androids of Tara and the eerie poise of The Stones of Blood for brawny location filming and the programme’s biggest monster. The marshes look great, Tom Baker and Romana keep the centre steady, and the “company vs. cult” tensions hum; but the script’s broad strokes and repetitive siege beats leave it trailing the run’s upper tier.

In the season’s ledger it sits below the exuberance of The Pirate Planet and well under the gothic touchstones like Pyramids of Mars: a lower-mid-tier entry whose scale and sincerity can’t quite mask its rough edges.

Continuity-wise, it stitches the arc together with workmanlike clarity. The White Guardian’s commission from The Ribos Operation continues, the tracer’s glow finds the penultimate segment, and the stage is set for the reckoning of The Armageddon Factor. Its colonial capitalism and “progress as predation” themes converse with earlier cautions in The Mutants and The Green Death, while its “science as idol” thread nods to The Face of Evil and the myth-tech experiments around Underworld.

Taken as the breath before the finale, The Power of Kroll does its duty: it widens the quest’s canvas, tests the Doctor–Romana–K9 rhythm in harsher light, and hands the season off to its endgame: mud on its boots, mission intact.

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