The Seventh Doctor and Mel arrive at the Needle, a futuristic settlement run by [[MasterComputer the computer Whitenoise]], and immediately discover a murder. An impossible murder, as it turns out, since the citizens of the Needle have chips in their brains preventing them from committing any act of violence. But recently some citizens have been experiencing the phenomenon called "redlining" -- getting violent hallucinations that cause them to become obsessed with the colour "red. red. red. red. red. red. red. red."

Investigating the murders is Chief Blue, with the help of Whitenoise, although Blue is just as interested in watching the murders as he is in solving them. Meanwhile, a young woman named Celia Fortunaté realises that Whitenoise has been editing her memories, and begins to suspect -- correctly -- that she's redlined. Since her improbably good hacking skills would enable her to hack into Whitenoise, she confers with Needle matriarch Vi Yulquen about the possibility of staging a revolution against the editing. Yulquen, for her part, would like to forget the whole thing and just wants to spend time with Celia. She's perfectly happy just living her life among the IdleRich and supplying Slow -- a drug -- to the people outside the Needle.

While the Doctor is immediately captured and carted off to be chipped, Mel falls out of the Needle and lands on the dirigible of Draun, one of Yulquen's clients. Mel becomes paralyzed and is forced to trust Draun, even when he tries to cut her with his knife, "Little Babe". Draun believes that his new friend "Red" is from the Needle, and wants Mel to experience violence for the first time, just to show her what the world is like -- after all, Needle people only see violence on their SnuffFilm tapes. When Mel (fighting back) explains that she's not from the Needle at all, and that she doesn't even have a chip, Draun is utterly fascinated. He takes her to his sister, Nuane. Mel agrees to take the neuro-drug Slow, since it not only enhances the mind, but also repairs the nervous system by bonding with it. Nuane explains that she herself was a sort of "doctor" once, but that as soon as people left the Needle and regained the ability to commit violent acts, those in charge of medicine started performing terrifying experiments just because they ''could''. She herself is deeply ashamed of the things she's done. While Mel experiences the haze of Slow, Drain begins to redline and gets fixated on Mel's hair, and hopes to destroy the "red. red. red. red. red. red. red. red." Nuane and Mel manage to neutralise him, helped by the Doctor, who becomes psychically linked to Draun during the redline. Draun is shocked by his own actions, and he and Nuane agree to take Mel to Yulquen.

She recovers, and Draun and Nuane explain the structure of this society. Long ago, people had themselves chipped to prevent violence. But some people didn't want the computer to rule their lives, and moved outside the Needle, their capacity for violence restored. Those inside the Needle continued their perfect peaceful lives, bottling up their violent urges and never able to express them. But everyone, in or outside the Needle, remained chipped and watched by Whitenoise, and had their senses dulled. Slow is the only way to get back some feeling.

The Doctor, now chipped, redlines almost immediately and becomes psychically linked to people murdering each other across the Needle. The experience rather severely breaks him. He meets Celia, notes that she doesn't seem to ''belong'' in this society, and the two of them figure out that Whitenoise has been editing out all memory of the people who have been murdered. Meanwhile, Blue watches it all.

The Doctor and Celia confront Chief Blue and Whitenoise, and eventually discover that Celia isn't from the Needle at all. She's a human time traveller who landed in the Needle by accident. Her time travel mechanism is fully organic and part of her nervous system -- which is why Whitenoise accidentally went mental as soon as Celia was chipped. The Red originated with her, latched on the dangerously suppressed violent urge of the citizens and spread across the Needle, resulting in thousands of murders that Whitenoise covered up to preserve the peace. Celia's memory was simply edited. The Red drew the Doctor and the TARDIS towards him, since they're time-sensitive beings, and the Doctor started constantly redlining as soon as he was chipped due to his BizarreAlienBiology. Celia's ability to hack into Whitenoise is a result of her nervous system being integrated with her time travel device. Celia traps the Red inside her and commits HeroicSuicide, only for everyone else to realise it was a SenselessSacrifice -- the Red is still there. Whitenoise, who's actually pretty friendly, is willing to help, but will need to be fully disabled in order to destroy the Red... which it isn't willing to do.

Mel, Draun and Nuane finally visit Yulquen, who's morbidly fascinated by Mel's ability to ''feel'' and to ''hurt'' people. She's willing to help, but only if Mel agrees to severely harm her. Mel won't have it, and Yulquen reveals both her love for Celia and her past (very dysfunctional) relationship with Nuane. When the Doctor and Blue are finally able to contact Yulquen, Mel is able to hack into Whitenoise while the Doctor takes Slow and begins a BattleInTheCenterOfTheMind with the Red. Blue dies in the process (with a very nasty pop), but the Red is neutralised, Whitenoise is disabled and the citizens of the Needle are free to live their lives without being watched or edited. Yulquen isn't sure if she ''can'', but Nuane is willing to offer her another chance -- if not at a relationship, then at least at a normal life.
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!!Red contains examples of:
* AxCrazy: What happens to those possessed by the killer, euphemistically referred to as "redlining".
* BenevolentAI: Whitenoise is genuinely trying to do its job, and isn't evil or mad in the way most renegade computers in sci-fi tend to be.
* BloodSport: Simulations of this are apparently an approved form of entertainment for citizens of the Needle, despite the limitations on violent thoughts.
* BodySurf: The Red travels from person to person, feeding on their repressed violent urges and inciting them to cause harm.
* BondageIsBad: Played with a bit; Vi Yulquen is a wannabe masochist, and not a very nice person, but it's implied that her obsession is a product of her repressed society which stifles both pleasure and pain.
* CharacterizationMarchesOn: In some past Creator/BigFinish episodes, homosexual relationships were sometimes used as a punchline, even if the author of the episode was gay (e.g. Creator/MarkGatiss). But since the introduction of Iris' gay companion Tom to Creator/BigFinish, queer people have consistently been portrayed as just regular characters, and a subplot involving gay relationships becomes important in "Red" without being seen as strange by anyone-- there is a strongly implied attraction between Celia and Yulquen, and hints of a past relationship between Yulquen and Nuane.
* DarkerAndEdgier: Deals with some pretty adult themes for a ''Series/DoctorWho'' story.
* TheEvilsOfFreeWill: To ensure a peaceful society, citizens of the Needle are controlled via nanochip, and any thoughts of violence (as well as pleasurable urges, which are "precursors to violence") are "edited" from their minds. Unlike in most examples, however, the residents are free to leave at any time and most choose to stay because it is simpler not to have to be responsible for their actions.
* FantasticDrug: Slow, which affects the user's perception of time, enhances feeling, and can rapidly repair any physical injury.
* ICallItVera: Draun's knife, "Little Babe".
* TheKillerInMe: Literally. Celia Fortunatè is revealed to be the carrier of the Red, which was created when her capacity for violence corrupted Whitenoise's systems.
* MadnessMantra: "Red. Red. Red. Red. Red..."
* SnuffFilm: The Red Tape, a video record of each of the killings in the Needle. Blue delights in watching it.
* TrillingRs: Creator/SylvesterMcCoy stars in a story about people getting stuck on a MadnessMantra of "rrrrrrrrrred".
* UnPerson: Everyone who gets murdered.
* UtopiaJustifiesTheMeans: According to Whitenoise.
* TheVirus: The Red.
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