The Doctor exiles himself to the planet Torrok, hoping to avoid the bleak future he saw waiting at his trial. Torrok is a poverty-stricken urban wasteland, its sole industry -- the Torrok Television Corporation -- having been put out of business by the rival Meson Broadcasting System; the people spend their days indoors, watching mindless programming on MBS while robot Peace Keepers and violent gangs of Watchers roam the streets outside. Despite his best efforts not to get involved, the Doctor is once again contacted by the Time Lords, who order him to travel to the MBS satellite but do not explain what he is to do there, in order to maintain deniability should anything go wrong. When the Doctor refuses, the Time Lords alert the Peace Keepers to the Doctor’s illegal presence on their world, giving him no choice but to return to the TARDIS. He is accompanied by a young woman named Angela who had ventured out of the prison of her home, seeking adventure in the outside world. Since there is nothing to keep her on Torrok, he agrees to let her go with him -- but remains mindful of Peri’s apparent death, and is thus unwilling to let Angela walk into danger. The Time Lords remote-pilot the TARDIS to a derelict spaceship, dead in space near the MBS satellite, and then shut the TARDIS down, apparently to prevent the Doctor from departing before he’s finished his task. The Doctor transmats to the station, telling Angela to remain on the ship until he’s sure it’s safe to follow -- but moments after his departure, something drills through the ship’s hull and kills her.

As MBS has grown over the years, the station has become large and unwieldy, and the frequent orbital changes needed to keep it within range of all of the planets in the system have become dangerous operations. After the latest Move, chief engineer Terry Marston attends an illicit tryst with actress Mae Jordan, who is living with soap star Raymond Day but feels that Marston can help her career. Day, meanwhile, is fired for showing up drunk and flubbing his lines on a live broadcast of Jubilee Towers, and complains to the Programme Controller’s secretary Giselle. She advises him to try blackmailing Paradox Pictures executive Dominic Shepherd about his mysterious new project, Time of Your Life. In fact, Giselle wants the information for herself; she runs the entire station from her desk, and sits at the centre of a web of surveillance and manipulation which she regards as the ultimate form of interactive television. Day returns home, catches Marston and Jordan together, and shoots Marston dead in a fit of rage. Giselle, delighted by this plot twist, ignores the increasingly frantic calls from Marston’s assistant Jak Martyn; due to a glitch in the computer system, the recent Move has put the station on a collision course with a derelict ship, and it appears that the Move itself did not go entirely according to plan. If this is not sorted out soon, the station will hit the derelict and then fall into the sun.

The Doctor joins a tour group to avoid the station’s trigger-happy security guards, and sees a pair of Xyrons -- robot props from the science fiction series Timeriders -- grab two tourists and drag them off, kicking and screaming. The tour guide claims that this is a publicity stunt, but in fact it’s the result of another computer glitch. The Doctor then hops into the office of executive Firn Kaerson, again to avoid a security patrol, and Kaerson takes advantage of his arrival to shoo out his guests -- Miriam Walker and her associate Glynda from the Campaign for the Advancement of Television Standards, who wish to complain about the sex and violence in MBS programming. The Doctor, still unsure why the Time Lords have sent him here, asks Kaerson to describe any recent odd events or technological advances, and Kaerson tells him of the invention of the Marston Sphere, a dimensionally transcendental chamber used in Option-8’s duel-to-the-death game show Death Hunt 3000. According to rumour, Paradox Productions have pirated the technology for use in a secret project of their own.

The Doctor concludes that the Time Lords have sent him to prevent this potentially dangerous technology from being misused, and decides to begin his investigation at Paradox Productions. He is arrested by the brutal guard Dan Brookes before he can get far, but the station’s security chief, Anson Hammond, releases him, hoping he can help her to deal with the manipulative Giselle. Hammond advises the Doctor to contact Raymond Day and enlist his help to get to Shepherd, but what she doesn’t know is that Giselle has been spying on their conversation. Giselle thus contacts Paradox, warns them that someone is trying to put an end to their latest TV project, and negotiates a deal to have the newcomer killed. Amused by the irony, she contacts Hammond anonymously -- as she has done before -- and orders her to kill the Doctor. Hammond, threatened with death by her unknown employer if she refuses to obey, has no choice but to set off in search of her former ally…

Several star systems away, in the plasterboard city of Neo Tokyo, computer programmer Grant Markham becomes suspicious of the remarkably advanced technology being supplied to New Earth by his employers, the Network. He and his friend Stuart Revell hack into the Network to find out where the technology is coming from, but are caught by a security programme which destroys Grant’s computer with a power spike. While Stuart heads home to ponder what they have discovered, Grant checks through the files they managed to print and finds a string of characters which appears almost like phonetic speech. Stuart’s train is suddenly derailed on its way home when an impenetrable barrier appears around Neo Tokyo, and, unable to reach his home outside the barrier, Stuart returns to Grant’s -- to find that Grant has been taken prisoner by a man in a superhero costume. Other people in superhero costumes appear and begin fighting with the man who has taken Grant prisoner, and as Grant and Stuart flee, Grant claims that the man in the costume was his boss, Dominic Shepherd. At that point things get truly bizarre, as a Godzilla-like monster suddenly appears in the downtown core and begins running amok.

A party of Timeriders fans barricade themselves in the Programme Controller’s office to protest the cancellation of their show, unaware that thanks to Giselle’s efforts the Programme Controller has not been on the station for months. Giselle locks them in and forgets about them while she monitors the Doctor’s progress, closing bulkheads to redirect his route and thus give Hammond a chance to catch up to him. The Doctor, realising that he is being toyed with, catches a security camera and wires the system to ignore his presence, but is then shot by the robot action star Bloodsoak Bunny, which didn’t register a living presence within range. The film crew tends to his wounds and makes him sign a waiver testifying that he deliberately ignored the warning signs, and due to the delay, Hammond is waiting for him by the time he reaches the Loop. Just as she is about to shoot him, Giselle’s surveillance monitors cut out, and she fails to see that Hammond has chosen to let the Doctor live, although she knows that this means Brookes will be sent to kill her.

Martyn finally gets through to Giselle, to warn her that the system glitches they have experienced are side-effects of a virus which has infected the satellite’s computer network; due to corporate espionage between the rival stations and the haphazard programming of the computer net, the virus has been causing random malfunctions as it worms through the systems. And now it has achieved its objective -- the docking bay controls are under the control of an entity called KRLLXK, which locks Giselle out of the net, telling her that “all organic bugs will be purged”. She and Martyn are helpless to act as the “derelict” ship comes to life and approaches the docking bay…

One of the “superheroes” in Neo Tokyo is crushed to death while confronting the dinosaur, due to a glitch in the teleport which should have whisked her to safety a moment before the dinosaur stepped on her, and Shepherd is forced to return to the station to investigate. Elsewhere on the station, Day and Jordan try to dispose of Marston’s body, only to be attacked by a malfunctioning Xyron. The Xyron carries Day around the corner and then drops him, which is all it was programmed to do as a prop; but by the time he and Jordan get away from it, another Xyron has carried away Marston’s body and hidden it. Meanwhile, the “derelict” ship enters the docking bay, bringing with it a technorganic entity which buries its tentacles in the station’s infrastructure and begins sucking raw data out of the computer net.

The Doctor, still lost, meets Miriam Walker, who helps him to reach Paradox when he tells her that he’s trying to get one of their programmes cancelled. Upon arriving at Paradox, he tries to confront Shepherd about his use of the Marston Spheres, but Shepherd shoots him with a stunner. Day then arrives, and since Shepherd now has more important things to worry about, he strikes a deal with Day, offering him his old job with an increased salary if he remains silent about the Doctor’s presence. Day accepts the offer, and Shepherd has the unconscious Doctor shipped off to the Death-Hunt 3000 studios, to dispose of his problem while simultaneously embarrassing a rival studio.

The Paradox film crew, realising that Time of Your Life is out of control, transmat a giant robot into Neo Tokyo to attack the dinosaur and provide closure to their programme. The robophobic Grant recognises the robot’s chanting as the character string he downloaded earlier, and realises that the Network is responsible for what is happening here. He and Stuart thus break into the Network building, where Grant tries to shut down the robot and dinosaur while Stuart tries out a pair of VRTV goggles, advanced technology which provides realistic immersion within the TV viewing environment. Grant discovers that the programmes controlling the dinosaur and robot are in a separate but linked computer net, but the moment that he hacks into the new system, a carnivorous bird appears in the VRTV environment and consumes Stuart’s mind. Shepherd detects the intrusion, returns to Neo Tokyo and kidnaps the stunned Grant, taking him back to Paradox. Grant, listening to the panicked technicians, works out that his home city has been transported into a Marston Sphere as a realistic setting for a safari game show. Shepherd set up the Network to sell VRTV to the people of Neo Tokyo both as a sideline and as a front to cover his work in setting up the exclusion zone. Grant’s discoveries threaten to expose him, however, and realising that he is in danger, Grant flees into the depths of the station while Shepherd is occupied dealing with the malfunctions caused by Krllxk’s virus.

As the Death-Hunt 3000 contestants are transported into the Marston Sphere, another transmat glitch causes a transport to materialise in the back row of the audience, killing everyone seated there. As Kaerson and Miriam Walker take charge of the evacuation, Kaerson sees the Doctor inside the sphere, but when he tries to rescue him he finds that the transmat has completely shut down. Inside the sphere, the Doctor is forced to battle the warrior Anjor, who kills for the thrill of it -- but as they do battle the Doctor collapses, attacked through the VRTV implants which connect his mind to those of the studio audience. Anjor, noticing that the cameras have stopped transmitting, realises that something has gone wrong and allows the Doctor to live. The Doctor awakens with the understanding that something has invaded the MBS computer net and is feeding on all of the data it encounters, including any minds connected to the VRTV network. He now realises that the Time Lords sent him here to prevent the invader from killing everyone aboard MBS, but he was too arrogant and self-occupied to understand the real danger until now… when it may be too late to do anything about it.

Giselle sends Martyn and a patrol of security guards to dispose of the invader, but it kills them and seals off the docking bay. Realising that the situation is officially out of control, Giselle arranges a secret evacuation, contacting only those who will be in a position to help her career when they return to Meson Primus. But before she can finish compiling the data she will need to blackmail them, Hammond arrives and takes her hostage so she can get off the station. Brookes finds and attacks Hammond as they approach the escape pods, however, and while they fight, Giselle flees back to her office for the data she requires -- only to find that those she trusted with news of the evacuation have told their friends, who have told their friends in turn. All of the escape pods have already departed, and although the opportunistic Mae Jordan is amongst those who have escaped, everyone else aboard the station -- including Giselle and Dominic Shepherd -- is trapped with no way out as the datavore’s hold over the net grows stronger.

While making their way to the edge of the Sphere, the Doctor and Anjor are attacked by a H’arthi, a cybernetically augmented wolf which tastes their blood and marks them as targets. The Doctor uses the sphere’s control box to overlap its interior and exterior space, and escapes along with Anjor -- but he has seriously underestimated the H’arthi’s determination, and it makes the leap itself into the station. There, although it is struck and mortally injured by a Loop train while searching for its prey, it refuses to give up the hunt…

The Doctor and Anjor return to the Option-8 studios, where Nik Calvin, the oddly calm host of Death-Hunt 3000, is watching as the Sphere’s dimensional resonance continues to fluctuate due to the continuing computer glitches. The Doctor fixes the problem before the Sphere’s external and internal dimensions can overlap and destroy the station, but realises that the sphere in the Paradox studio will be suffering from the same problem. As he and his allies head for Paradox, they run into Grant and Raymond Day, who have barely escaped from the H’arthi in the Loop system. The Doctor orders Day to send a message on the station’s internal communications system, telling everyone who is still alive to come to the Paradox studios.

In the Paradox studios, the Doctor uses VRTV goggles to operate the Sphere’s fail-safe protocols, and sends Neo Tokyo back where it came from before Grant can tell him that he was supposed to be inside. Now that the Sphere is empty again, the Doctor intends to use the fail-safe to transport the survivors to Meson Primus -- but before he can do so, Krllxk completes its work and seizes control of the station’s computer systems. Every mechanical object on the station becomes a killer, including the many robots used in the TV shows. Dominic Shepherd is flung down a waste disposal shaft by a Xyron, and the lovable android from a family sitcom attacks Miriam Walker’s assistant Glynda, shoving her head into a fountain of boiling water. Day is pursued by an animatronic knight, and while searching for a hiding place he trips over Terry Marston’s body, allowing the knight to catch up and decapitate him. The lighting system is flooded with oil and blows up, immolating several unlucky people, and the Loop trains collide head-on, killing many more. Hammond and Brookes must join forces to escape from the attacking androids, but when Brookes tries to sacrifice Hammond to save his own life, Hammond shoots him. She then tries to send out a distress call, but Krllxk attaches a virus to the outgoing signal, destroying the ship which answers the call.

Giselle, finally understanding that she’s now part of what is happening here instead of merely an observer, releases the terrified Timeriders fans from the Programme Controller’s office and tries to help them escape. Most of the survivors make it to the Paradox studios, but Anjor is killed by the H’arthi when he leaves to collect the stragglers. The Doctor electrocutes the H’arthi but damages the teleport systems in the process, and is forced to transport the survivors to Torrok instead of Meson Primus. Still hoping to save the remaining survivors, he uses the VRTV goggles to communicate directly with Krllxk, and is horrified to find that it has absorbed Angela into itself. However, her memory of the Doctor gives him a link with which to speak to Krllxk, an artificial life form which turned on its creators when it became convinced that they were hiding the secret of Life from it. It has accepted all of the data in the MBS transmissions as fact, including the fictional output of the networks in which violence is accepted as a natural and fun part of life, and it therefore intends to kill every living being who has hidden the secret of life. Due to the glitches Krllxk caused during the last Move, however, the MBS station is falling into the sun and will be destroyed within minutes. Krllxk is forced to deal with the Doctor to ensure its own survival, and the Doctor agrees to allow it into the TARDIS if it allows him to evacuate the remaining survivors. As soon as everybody is aboard the TARDIS, however, he reneges on the deal and locks Krllxk out. Once the station is destroyed by the heat of the sun, the Time Lords restore the power of flight to the TARDIS -- but the Doctor then realises that game show host Nik Calvin is in fact an android into which Krllxk has uploaded itself. Krllxk attempts to transfer itself into the TARDIS console, and the Doctor is forced to beat it to death with the TARDIS hatstand to prevent it from gaining mastery of space and time.

Those whom the Doctor transported via the Marston Sphere are surprised to find themselves on Torrok, and are even more surprised to be attacked by the Peace Keepers, charged with illegal immigration and breaking curfew. The Watcher gangs also attack them for trespassing on their turf, and as the battle rages, Giselle comes into her own, using her skills to direct the fighting. She and Hammond join forces to beat back the Watchers and Peace Keepers, thus gaining access to the abandoned Torrok Television Corporation station; there, Grant and Kaerson shut down the Peace Keepers, bringing peace to Torrok at last. The destruction of MBS has deprived the people of Torrok of the soul-numbing television which had dulled their ambitions, and with the help of the evacuees they prepare to relaunch the TTC; with Miriam Walker to guide them, they will bring quality, educational programming back to television. The Doctor, accepting that the contemplative life is not for him, leaves them to build their new world, but takes with him a new companion -- Grant Markham.