Book 1: Europe After the Reign
On Guy Fawkes Night in London in 1997, a financially desperate 16-year-old, Evey Hammond, sexually solicits men who are actually members of the state secret police, called "The Finger". Preparing to rape and kill her, the Fingermen are dispatched by V, a cloaked anarchist wearing a Guy Fawkes mask, who later remotely detonates explosives at the Houses of Parliament before bringing Evey to his contraband-filled underground lair, the "Shadow Gallery". Evey tells V her life story, which reveals that a global nuclear war in the late 1980s has since triggered the rise of England's fascist, white supremacist government, Norsefire.
Meanwhile, Eric Finch, a veteran detective in charge of the regular police force—"the Nose"—begins investigating V's terrorist activities. Finch often communicates with Norsefire's other intelligence departments, including "the Finger," led by Derek Almond, and "the Head", embodied by Adam Susan: the reclusive government Leader, who obsessively oversees the government's Fate computer system. Finch's case thickens when V mentally deranges Lewis Prothero, a propaganda-broadcasting radio personality; forces the suicide of Bishop Anthony Lilliman, a paedophile priest; and prepares to murder Dr. Delia Surridge, a medical researcher who once had a romance with Finch. Finch suddenly discovers that the connection among V's three targets: they all used to work at a former Norsefire "resettlement camp" near Larkhill. That night, V kills both Almond and Surridge, but Surridge has left a diary revealing that V—a former inmate and victim of Surridge's cruel medical experiments—was able to destroy and flee the camp, and is now eliminating the camp's former officers to keep his true identity hidden. Finch reports these findings to Susan, who suspects that this "vendetta" is actually just a cover for V, who, he worries, may be plotting an even bigger terrorist attack.
Book 2: This Vicious Cabaret
Four months later, V breaks into Jordan Tower, the home of Norsefire's propaganda department, "the Mouth"—led by Roger Dascombe—to broadcast a speech that calls on the people to resist the government. V escapes using an elaborate diversion that results in Dascombe's death. Finch is soon introduced to Peter Creedy, the crooked new head of the Finger, who provokes Finch to strike him and thus get sent on a forced vacation. All this time, Evey has moved on with her life, becoming romantically involved with a much older man and petty criminal named Gordon. Evey and Gordon unknowingly cross paths with Rose Almond, the widow of the recently killed Derek. After Derek's death, Rose reluctantly began a relationship with Dascombe, but now, with both of her lovers murdered, she is forced to perform demoralizing burlesque work, increasing her hatred of the unsupportive government.
When a Scottish gangster named Ally Harper murders Gordon, a vengeful Evey interrupts a meeting between Harper and Creedy, the latter of whom is buying the support of Harper's thugs in preparation for a coup d'état. Evey attempts to shoot Harper, but is suddenly abducted and then imprisoned. Amidst interrogation and torture, Evey finds an old letter hidden in her cell by an inmate named Valerie Page, a film actress who was imprisoned and executed for being a lesbian. Evey's interrogator finally gives her a choice of collaboration or death; inspired by Valerie, Evey refuses to collaborate, and, expecting to be executed, is instead told that she is free. Stunned, Evey learns that her supposed imprisonment is in fact a hoax constructed by V so that she could experience an ordeal similar to the one that shaped him at Larkhill. He reveals that Valerie was a real Larkhill prisoner who died in the cell next to his and that the letter is not a fake. Evey forgives V, who has hacked into the government's Fate computer system and started emotionally manipulating Adam Susan with mind games. Consequently, Susan, who has formed a bizarre sexual attachment to the computer, is beginning to descend into madness.
Book 3: The Land of Do-As-You-Please
The following 5 November (1998), V blows up the Post Office Tower and Jordan Tower, effectively shutting down three government agencies: the Eye, the Ear, and the Mouth. Creedy's men and Harper's associated street gangs violently suppress the subsequent wave of revolutionary fervor from the public. V notes to Evey that he has not yet achieved what he calls the "Land of Do-as-You-Please", meaning a functional anarchistic society, and considers the current chaotic situation an interim period of "Land of Take-What-You-Want". Finch has been mysteriously absent and his young assistant, Dominic, one day realises that V has been influencing the Fate computer all along, which would explain V's consistent foresight. All the while, Finch has been travelling to the abandoned site of Larkhill, where he takes LSD to conjure up memories of his own devastated past and to put his mind in the role of a prisoner of Larkhill, like V, to help give him an intuitive understanding of V's experiences. Returning to London, Finch suddenly deduces that V's lair is inside the abandoned Victoria Station, which he enters, shooting V repeatedly, though V claims he cannot be killed since he is only an idea and that "ideas are bulletproof". Regardless, V is indeed mortally wounded and returns to the Shadow Gallery deeper within, dying in Evey's arms. Evey considers unmasking V, but decides not to and instead assumes V's identity, donning one of his spare Guy Fawkes costumes.
Meanwhile, Creedy has been pressuring Susan to appear in public, hoping to leave him exposed. Sure enough, as Susan stops to shake hands with Rose during a parade, she shoots him in the head. Despite V's death, his plans are already in motion, resulting in Creedy (now in charge of The Finger), Harper, and Conrad Heyer (in charge of The Eye) all turning against and fatally wounding each other. This leaves Finch as the only survivor among the top government officials, but he freely abandons his post, largely due to his LSD-influenced change of outlook. Next, Evey appears to a crowd, dressed as V, announcing the destruction of 10 Downing Street the following day and telling the crowd they must "...choose what comes next. Lives of your own, or a return to chains", whereupon a general insurrection begins. Evey destroys 10 Downing Street by blowing up an Underground train containing V's body, in the style of an explosive Viking funeral. She abducts Dominic, apparently to train him as her successor. The book ends with Finch quietly observing the chaos raging in the city and walking down an abandoned motorway whose lights have all gone out.