Doctor Who The Horns Of Nimon Part 1

The declining Skonnan Empire is under control of a mysterious horned being called the Nimon. It resides inside a labyrinthine Power Complex on the planet Skonnos, and communicates only with the Skonnan leader, Soldeed, who reveres the Nimon as a god. The Nimon demands a regular tribute of young people, who are flown in from the nearby planet Aneth, as well as a supply of hymetusite crystals.

A transport ship bearing the sacrifices from Aneth breaks down and becomes stranded in interplanetary space, close to a black hole. Outside the ship, the TARDIS materialises. The Fourth Doctor attempts to save the TARDIS from being drawn into the black hole by attaching it to the Skonnan ship with a force field. He and Romana then board the ship, leaving K9 behind. Once aboard they find a cargo of hymetusite crystals and a hold full of young prisoners from Aneth, led by Seth. The Doctor and Romana are captured at gunpoint by the co-pilot, who forces them to fix the ship using a hymetusite crystal. The Doctor returns to the TARDIS to get supplies, and becomes stranded when the ship's engines start. Steering the TARDIS away from the black hole, he travels to Skonnos.

On Skonnos, the Nimon is enraged by the delayed sacrifice and threatens to withhold the promised armaments that will help rebuild the Skonnan Empire. The ship arrives, bearing the sacrifices and Romana, who are forced to carry the hymetusite crystals into the Power Complex. Within the labyrinth, the walls seem to shift and change, forcing them towards the Nimon. They discover desiccated husks of bodies, previous Anethans who have been drained of life. They meet the Nimon, who has the power to fire deadly laser beams out of his horns. Meanwhile, the TARDIS has materialised on Skonnos. The Doctor enters the labyrinth and distracts the Nimon, enabling Romana, Seth and Teka to escape.

In the centre of the Power Complex, the Nimon operates a transit system, opening a tunnel through a pair of black holes. Large globes carrying two more Nimon appear. It is revealed that the Nimon are a parasitic race who travel via artificial black holes between planets, draining their resources, before moving on to conquer new worlds. They refer to this as "the Great Journey of Life". They are now abandoning the distant Planet Crinoth to take over Skonnos. Soldeed questions his faith when confronted with multiple Nimons. Romana accidentally travels through the tunnel to Crinoth, which she finds overrun with Nimons. She is assisted by an old man named Sezom, who gives her a mineral called jacenite which can be used to destroy Nimons. Sezom admits that he was the one who helped the Nimons take over, falling for their promises (much like Soldeed). He realized too late that the small tributes were only the start of destruction of the whole population.

Romana is brought back to Skonnos. Amid a struggle, Seth has taken Soldeed's weapon, a ceremonial staff, and fitting it with the jacenite, he stuns the Nimons. K9, who has been held captive in Soldeed's laboratory, shoots the remaining Nimon. Soldeed is also shot by Seth, but sets off a self-destruct system to destroy the Power Complex. Guided by K9, the Doctor and his party escape from the labyrinth. The Skonnans evacuate their city as the Nimon Power Complex explodes. Seth and Teka take a spacecraft to return to Aneth, while the Nimon-infested Crinoth disintegrates.