Lolita is a novel about an intellectual pedophile named Humbert Humbert who becomes infatuated with a 12-year old girl, Lolita. After renting a room from Charlotte, Lolita's mother, Humbert marries Charlotte. Charlotte dies after being hit by a car and Humbert becomes Lolita's step-father, entering into a sexual relationship with the girl and traveling around the country. After Lolita disappears, Humbert finds her years later with a husband. Humbert then finds and kills Quilty, a playwrite, who took Lolita away from him.
Humbert Humbert, a European literary scholar, describes the premature death of his childhood sweetheart, Annabel Leigh. He suggests his unconsummated love for her caused his fixation with nymphets (girls aged 9–14) and indulges in his sexual fantasies by pretending to read a book in a public park and being aroused by nymphets playing near him, as well as by visiting a prostitute who he believes is 16 or 17, and imagining her to be three years younger. After a misadventure when he requests a nymphet-agedgirl from a pimp, Humbert marries an adult woman with childish mannerisms, Valeria, to allay suspicion. His marriage with Valeria dissolves, after she admits to having an affair with a Russian taxi driver. Humbert wants to kill her, but Valeria and the taxi driver leave before he gets the chance. After another visit to a psychiatric ward after a mental breakdown, he moves to the small New England town of Ramsdale to write.
Humbert fantasizes about meeting and eventually molesting the 12-year-old daughter of an impoverished family, the McCoos, from whom he agreed to rent an apartment. Upon his arrival in Ramsdale, however, he discovers that their house has burned down. A landlady named Mrs. Charlotte Haze offers to accommodate him instead, and Humbert visits her residence out of politeness. Humbert plans to decline Charlotte's offer until he sees her 12-year-old daughter, Dolores (born 1935), known as "Lo," "Lola," or "Dolly". He becomes infatuated with her, in part because of her uncanny resemblance to Annabel, and agrees to stay at Charlotte's house only to be near her daughter, whom he privately nicknames "Lolita".
Humbert starts a diary in which he keeps detailed descriptions of Lolita's characteristics, along with moments that they spend together. The diary also contains hateful comments about Charlotte, along with a description of a picture in a magazine of a playwright (Clare Quilty), who Lolita has a crush on and who Humbert resembles.
Charlotte, Lolita, her friend Mary, and Humbert plan to go to Hourglass Lake for a picnic one Sunday. However, Mary's mother phones to tell them that Mary is running a fever and that she can't go. Mrs. Haze postpones the picnic and, as a result, Lolita refuses to go to church with her. Mrs. Haze leaves for church and Humbert and Lolita are left alone. While the two sing a song, Humbert secretly ejaculates in his pants as Lolita sits on his lap. She does not notice and leaves for the movies. After returning from a lunch in town, Charlotte tells Humbert that Lolita is going to camp Thursday and she won't return until the next school year.
That Thursday, before getting in the car, Lolita runs back into the house and kisses Humbert goodbye. As Charlotte, who has fallen in love with Humbert, drives Lolita to summer camp, the housemaid delivers a letter to Humbert from Charlotte telling him that he must either marry her or move out to avoid embarrassment. To continue living near Lolita, Humbert agrees to marry Charlotte. After finding Humbert's diary and learning his true feelings, Charlotte confronts him, calling him a "detestable, abominable, criminal fraud". As Humbert goes into the kitchen to get them drinks, Charlotte runs out of the house with the letters that she had just written, but is killed by a passing car before she can mail them. A little girl gives Humbert the letters, and he later examines them: one was to Lolita telling her they were moving, another to a boarding school in which Lolita was to be enlisted, and a third to Humbert that suggested a possible reuniting between him and Charlotte in the future.
Humbert retrieves Lolita from camp, lying that Charlotte has been hospitalized, and takes Lolita to a hotel, where he plans to use a sleeping pill on Lolita and rape her while she is unconscious. As he waits for the pill to take effect, he wanders through the hotel and meets a man (Quilty) who inquires about Lolita. Humbert excuses himself from the strange conversation and returns to the hotel room. There, he finds that the sedative was too mild after seeing Lolita drifting in and out of sleep. He lies next to her all night, fantasizing about him and her together. However, it is she who initiates sex in the morning, showing him what she had learned at summer camp. On their way to the fake hospital that Charlotte was supposed to be staying at, Humbert tells Lolita that her mother is dead. Thereafter Lolita and Humbert drive around the country, moving from state to state and motel to motel. To keep Lolita from going to the police, Humbert tells her that if he is arrested, she will become a ward of the state and lose all her clothes and belongings. He also bribes her with food, money, or permission to attend fun events in return for sexual favors. After a year of touring North America, the two settle in another New England town, where Lolita is enrolled in a girls' school. Humbert becomes very possessive and strict, forbidding Lolita to take part in after-school activities or to associate with boys. The headmistress of the school sees his strictness as the concern of a loving, though old-fashioned, parent. Humbert reluctantly grants Lolita permission to join the school play in exchange for more sexual favors. The play she joins is written by Mr. Clare Quilty, but Humbert doesn't know it. Just before opening night, Lolita and Humbert have a ferocious argument, and Lolita runs away. Humbert searches frantically until he finds her bike next to the phone booth she was using. She brushes the phone call off and reconciles with him, saying she wants to go on another road trip with him, only this time she gets to choose where they go.
As Lolita and Humbert drive westward again, Humbert becomes suspicious that someone is following them, first thinking it's a cop and then later one of Lolita's admirers from school. Lolita falls ill and must convalesce in a hospital, while Humbert stays in a nearby motel. The hospital staff tells Humbert in the morning that her uncle checked her out. Humbert embarks upon a frantic search to find Lolita and her abductor, retracing his steps to every hotel that they'd been to thus far, but fails to track them. During his search, Humbert has a two-year relationship (ending in 1952) with a woman named Rita, whom he describes as a "kind, good sport" who "solemnly approve[s]" of his search for Lolita, while knowing none of the details.
Humbert receives a letter from Lolita, now 17, who tells him that she is married, pregnant, and in desperate need of money. Humbert tracks down the address and finds Lolita, but her husband is not the man that kidnapped her. He promises to give her money in exchange for the name of the man who abducted her. She reveals that Clare Quilty checked her out of the hospital and tried to make her star in one of his pornographic films; but expelled her upon refusal because she only wanted to be with Quilty. She worked odd jobs before meeting and marrying her husband, Dick, who knows nothing about her past. Although she looks much older now, Humbert realizes that he still loves Lolita and repeatedly asks her to leave Dick and go with him, which she refuses. He gives her $4,000, which is much more than what she asked for, and then leaves. As he leaves, she smiles and shouts goodbye as if he was her own father. Humbert tracks down the dentist who knows where to find Quilty, and later kills Quilty in his own mansion. Shortly afterwards, he is arrested for driving on the wrong side of the road and running a red light. The narrative closes with Humbert's final words to Lolita in which he wishes her well, and reveals the novel in its metafiction to be the memoirs of his life, only to be published after he and Lolita have both died. The novel's fictional foreword states that Humbert dies of coronary thrombosis after completing the manuscript, just one or two months after getting arrested. It also states that "Mrs. Richard F. Schiller" (Lolita) died giving birth to a stillborn girl on Christmas Day, 1952, at the age of 17, a month after Humbert's death on November 16, 1952.