In San Diego, in 1969, precocious William Miller learns that he is two years younger than his classmates. William’s older sister Anita feels repressed by their widowed mother Elaine’s eccentricities and decides to leave their “house of lies” to become an airline stewardess. Before going, Anita promises William that someday he will be “cool” and gives him her secret collection of rock music albums. Later, William finds a note from Anita saying, “Listen to Tommy with a candle burning and you will see your entire future.” In 1973, the fifteen-year-old William sends writing samples to Creem magazine editor and rock critic Lester Bangs and later talks with him in a café, where Lester laments the end of rock and roll. Impressed by William’s talent, Lester assigns him to cover a Black Sabbath concert, but warns him to avoid becoming friends with the musicians. Although Elaine is suspicious of rock music, she drives William to the concert, but cannot refrain from yelling out, “Don’t take drugs!” as she drives away. At the stage door, William is refused entrance. While he waits outside the door, he meets “Penny Lane,” an engaging and worldly young woman, barely older than he is, and her circle of female music fans she calls “Band-Aids.” Penny, who has renamed herself after a song, shares with him her idealistic views that their devotion to the music sets them apart from other groupies. When Stillwater, the opening band, arrives, William’s encyclopedic knowledge of the band gets him in the door to interview Black Sabbath. Although he is usually level-headed, William is thrilled to be part of the backstage scene and can barely contain his excitement, something Lester warned him about, and Penny gently advises him to “be cool.” After the concert, Stillwater’s lead guitarist, Russell Hammond, invites William to join them at the Hyatt House, a hotel in Los Angeles. Several days later, William hitches a ride to the hotel with Penny, who mysteriously evades talking about her life, other than her relationship with the rock scene. At the hotel, William watches her work her charisma on the gathering of musicians and fans that are partying there. Despite the air of sophisticated detachment she tries to maintain, William learns that she and Russell had a casual affair during the previous tour and that they are still drawn to each other, even though he has a girlfriend. William’s article about Black Sabbath gets the attention of Rolling Stone music editor Ben Fong-Torres, who, unaware that William is so young, assigns him to write a story about Stillwater’s road tour. Lester, whom William calls regularly for advice, encourages him to take the job. Elaine, a college professor who wants William to aim for law school, very reluctantly gives him permission to miss his high school classes and follow the band. After joining Stillwater and company on their tour bus, William tries to interview Russell and lead singer Jeff Bebe, but they elude him, fearing that he is “the enemy” who might make them look bad in print. Unable to get an interview, William stays longer than planned, causing the worried Elaine to call William repeatedly. The assortment of people, who answer the phone and who casually mention drugs and room sharing, adds to her uneasiness. William watches the band’s camaraderie dissolve when t-shirts advertising the tour are delivered. Disappointed that the shirt’s photograph blurs the features of everyone except Jeff, the bandmembers quarrel, exposing latent rivalry between Russell and the singer. After the concert, William accompanies Russell to a drug party held by local fans. Later, high on acid, Russell climbs to the garage roof and exclaims to the crowd, “I am a golden god.” The next day, on the bus, hostility is in the air, until someone begins singing along with the radio and the rest of the group joins in. Feeling the pressure to complete his story, William attempts to write, but is interrupted by three bored Band-Aids who decide to relieve him of his virginity. When Ben calls to demand the finished article, William quotes several intriguing phrases that he and Lester had prepared earlier, for just this sort of emergency, and convinces Ben to give him more time. During one of Elaine’s calls to William, Russell takes the phone and tries to reassure her, but she stuns him with a lecture about his “world of compromised values.” As the tour continues and Stillwater’s fame builds, a corporate manager courts them. After abandoning the bus, the band travels by plane and is lured by the new manager to replace their counter-culture values with material ones, prompting the observant William to remember Lester’s predictions about rock music’s loss of innocence. After witnessing a quirky poker game, in which Russell and the boys trade the unwitting Band-Aids to another rock band, William becomes torn between loyalty and disapproval. In an uncharacteristic confrontation with Penny, who has blinded herself to Russell’s ambivalence, William points out the superficiality of their situation, and in frustration, tells her that she has been sold for fifty dollars and a case of beer. Later, in New York City, Russell reunites with his girl friend Leslie, and Penny discovers she is excluded from the band’s activities. After pursuing her to the hotel, William finds that she has overdosed on Quaaludes. While keeping Penny alive until a doctor pumps her stomach, William admits aloud that he loves her. Later, after surviving the ordeal, Penny tells William about her life and her real name, Lady Goodman, then returns home to San Diego. The Rolling Stone editors order William to send what he has written for the fact-checker and then meet at their San Francisco office. The next day, the band’s plane is shaken by the great turbulence of an electrical storm. Fearing death, the passengers take turns confessing past sins. After revealing that he slept with Leslie, Jeff volunteers that Russell slept with Penny, but when he makes disparaging remarks about her, William heatedly accuses them all of using and discarding their biggest fan. After the plane safely lands, Russell, who has been thoughtfully quiet, tells William to “write what you want.” In San Francisco, the Rolling Stone staff is unhappy with William’s story, but gives him one night to finish the article. William calls Lester, who advises him to be “honest and unmerciful,” and that, “like booze,” the friendships he made can delude him into believing he is “cool.” In consolation, Lester points out that “uncool” people make great art out of their longings. Later, William’s completed article impresses his editors, until the fact-checker claims that Russell denies everything William wrote. At the airport on the journey home, the betrayed William encounters Anita, who braves a reunion with their mother to console him. Meanwhile, Russell calls Penny to apologize and offers to come see her, but she gives him William’s address instead of her own, and then leaves for Morocco, a place she had often talked about with William. Penny’s ploy succeeds in reconciling Russell and William, and Russell tells the Rolling Stone editors that William wrote the truth. When the magazine featuring William’s article hits the stands, Stillwater is on the cover.