Behind an artificial spatial anomaly lies the planet Zamper, where a race of genetically engineered telekinetic slugs is forced to build battleships which are sold to every species in the galaxy. The AI known as the Management runs the business end of Zamper, while the human Secunda oversees the day-to-day administration of the planet and its human staff. Mr Jottipher, Zamper’s cultural liaison, is there to make the guests of Zamper feel more at home and relaxed while their business is conducted. Since Zamper is technically located outside the galaxy, it is not subject to the galaxy’s revenue laws; thus, a call-in casino is operated from the planet’s surface, under the supervision of Taal and his inexperienced new assistant, Christie. The only other human on the planet is Dr Smith, a zoologist recruited by the Management to find out why the Zamps’ productivity has been declining over the past twenty-five years.
Two Chelonian officers, General Hezzka and First Pilot Ivzid, arrive on Zamper to purchase a battle cruiser for their falling Empire. Chelonia has recently fought a revolutionary civil war, and the deposed Big Mother plans to use the Zamp cruiser to reclaim his world from the usurper who dares to make peace treaties with lesser species. Ivzid tries to sneak a hand weapon into the business centre with him, a crime which normally merits immediate expulsion; however, the Secunda simply confiscates the gun and places it in the safe along with the Chelonians’ ten-million-livre deposit. Things are not well on Zamper, and the Secunda has her own plans for the gun.
The TARDIS materialises on a test ship programmed to crash on Zamper, and by the time the Doctor and his companions work out where they are, it’s too late to get back to the TARDIS and they are forced to jettison themselves in the ship’s escape pods. The Doctor and Benny land near Smith’s workplace, where Smith realises that they are unauthorised visitors -- proof of her suspicions that the Management is breaking down. There have been a number of inexplicable power failures recently, and Christie’s predecessor, Nula, was “accidentally” electrocuted after she spoke out against the Management in public. Meanwhile, Roz and Chris land near the main business concourse, and are welcomed in as friends; the Management, unable to explain their unannounced arrival, desperately concludes that it must have invited them all.
Roz, Chris and Benny bed down in Zamper’s guest quarters for the night while the Doctor works with Smith to solve the mystery of the Zamps’ declining production. Meanwhile, the power fluctuations continue, and the Management’s behaviour grows ever more erratic. Believing that the Management is on the point of total collapse, the Secunda convinces Mr Jottipher to help her steal the Chelonians’ shuttle and escape from Zamper at last. Hezzka, unnerved by the Zamps’ uncanny resemblance to a mythological horror from Chelonia’s past, suffers from bad dreams that night, and after another power failure strikes the centre he concludes that the mission is a failure and should be aborted. Ivzid sees this as weakness on his part, and sets off to complete the mission single-handedly, planning to steal the battle cruiser without paying for it. But when he reaches the cruiser which they’d been shown, he finds that it is a fake -- a hollow, empty shell.
The Doctor determines that the Zamps are a naturally telekinetic species, which were enslaved by the consortium which owns Zamper and genetically enhanced to become shipbuilders. Their communal herdmind has also been warped and linked to the Management, which keeps them under control; but somehow their subconscious instincts are breaking free, enabling them to act without the Management’s knowledge and perhaps evolve out of the consortium’s control. Smith reveals that she’s detected a new cavern in the tunnels beneath the concourse, and though the Doctor tries to investigate on his own, Smith soon realises where he’s gone and follows him. Together, they find that the Zamps have diverted the raw materials intended for the Chelonians’ battle cruiser and have constructed their own ship, which has been designed to carry their next clutch of eggs away from the planet. The Doctor regards this as a triumph of the spirit; after centuries of slavery, the Zamps are about to break free of the consortium’s control at last.
Hezzka concludes that his mission has failed, and tries to reclaim his deposit by activating Ivzid’s gun by remote control and blowing the lid off the Secunda’s safe. However, she has anticipated this and set Ivzid’s gun to maximum strength, and Hezzka brings down the ceiling on himself when he orders the gun to fire. The Secunda and Mr Jottipher flee to the Chelonians’ shuttle with the ten-million-livre deposit, and once there the Secunda tells Mr Jottipher to activate the shuttle so they can escape. He does so and is instantly killed by the anti-theft booby-traps, thus draining them of power and enabling the Secunda to pilot the shuttle to safety. Or so she thinks until she emerges from the spatial anomaly to find Big Mother’s entire fleet on the other side, waiting for Hezzka to return. The shuttle is tractored aboard the flagship, where the Secunda is interrogated and eventually dissected by a curious Chelonian surgeon-general.
The Management collapses completely, and Roz and Chris try to find the others and evacuate them to the TARDIS. “Christie”, however, turns out to be a mercenary who killed the real Christie and took her place, intending to infiltrate Zamper and steal the top-secret ship design plans. She tries to take Chris hostage and escape, but is injured when the Secunda shoots her to prevent anyone from interfering with her own escape. While Chris and Taal tend to her, Roz investigates the theft of the Chelonian shuttle -- but when she returns to the others to report, she finds that they’ve vanished. Drawn by some instinct to go downwards, she descends into the shipyards -- where she is captured by a monstrous beast which has captured Chris and Taal, and eaten Christie alive...
Benny finds Hezzka and tends to his injuries, and as they search for their missing companions, Hezzka comes to realise that he was wrong to consider the human race inferior. Meanwhile, Ivzid locates the cave containing the Zamps’ egg-carrier, and to the Doctor’s horror, he attempts to destroy them all by detonating the self-destructive bomb implanted in his body -- Strategy Z. Hezzka and Benny follow their instincts to the cave, just in time to see one of the Zamps split apart, revealing a monstrous new loop-like form which has been gestating inside. The Zamp-loop eats Ivzid alive and speaks to the others with the voice of the Management, which has now been co-opted to become the herdmind of the new Zamp species. The Zamps used the knowledge grafted into them by the consortium to force-evolve themselves into this new form; now, free of the consortium’s control, they have used their telekinetic powers to lure the Doctor and his friends here to witness their triumph, as they launch the egg-carrier and conquer the galaxy. The Doctor realises that this isn’t quite the triumph of life which he’d hoped for.
Fortunately, this Loop emerged from gestation prematurely in order to deal with Ivzid, and the others are able to escape from it. They rescue Roz, Chris and Taal from the other loop guard, and the Doctor orders them to return to the TARDIS while he uses the Chelonian shuttle’s abandoned escape pod to return to the fleet and warn them of the danger. The galaxy’s only hope is for the Chelonians to self-destruct their fleet and destroy the Zamp cruiser in the blast, saving the galaxy. More loops hatch out of the former Zamps and pursue the others back to the TARDIS, and Smith lags behind and gives her life to give the others time to reach a flyer. On their way back to the TARDIS, however, Hezzka succumbs to his injuries and dies. Chris tries to land near the TARDIS while evading the pursuing loops, but misjudges his landing speed and crashes, leaving himself and his injured friends at the mercy of the advancing loops...
The Doctor manages to contact Big Mother, who owes him a favour, as the Doctor once saved his life. Due to this debt of honour, Big Mother reluctantly accepts that the Doctor is telling the truth about the Zamp cruiser, but demands that the Doctor remain to die along with the fleet. The Doctor escapes, and the Chelonian Frinza, concluding that Big Mother has finally succumbed to senility, refuses to give the order to self-destruct based on the word of a parasite. The Zamp egg-carrier then emerges from the spatial anomaly, and the loops use their powers to freeze the Chelonian ships’ weapons systems and pick them off one by one. Frinza realises that the Doctor and Big Mother were right all along, and gives his life to route the flagship’s power through himself, temporarily bypassing the Zamps’ control. The self-destructive chain reaction wipes out the entire Chelonian fleet, destroys the Zamps and breaks the herdmind’s link with the Management.
The Doctor returns to Zamper, only to find that while the remaining loops died when their link with the herdmind was broken, Taal’s neck was broken in the crash. The Doctor takes Benny, Chris and Roz back to his house on Allen Road to recover from their injuries, and while relaxing, Roz finally comes to terms with her new life as a time traveller. She admits to the Doctor that while searching for the others she found a cavern full of unhatched loop eggs, and the Doctor promises to return to Zamper one day to deal with them. But first, he must deal with another problem which has caught his attention...
Source: Cameron Dixon