The novel is a standalone contemporary romance that alternates between the perspectives of Phoenix Walker and Lennon Michael, two teenagers from the small town of Hillcrest whose intense connection is shattered by betrayal, then rekindled years later under volatile circumstances.
The story opens four years before the main narrative. Phoenix, a teenager living in a decrepit trailer with his violent father, Vance Walker, who has an alcohol addiction, vows to escape Hillcrest through music. Phoenix's mother fled Vance's abuse when Phoenix was seven, leaving him behind.
The narration shifts to Lennon Michael, an eighteen-year-old senior at Hillcrest High and the daughter of Don Michael, a successful freelance songwriter who named her after John Lennon. Lennon's mother died minutes after her birth, and Don raised her alone. Lennon endures relentless fat-shaming from Sabrina Simmons, the popular captain of the dance team, and harbors a secret fascination with Phoenix.
When Lennon's English teacher asks her to tutor a failing student, the student turns out to be Phoenix. He walks out of their first session, but Lennon follows and hears him singing in the band room, recognizing his extraordinary talent. They begin meeting at the garage where Phoenix and his best friend, Reese "Storm" Storm, practice as a two-person band called Sharp Objects. Lennon discovers that Phoenix has undiagnosed dyslexia: He cannot process written text, but when she reads material aloud, he answers nearly all questions correctly. She buys him a reading pen that scans text aloud and persuades their teacher to let him use it during the final exam.
As they spend more time together, their bond deepens over shared stories of growing up without mothers. Lennon reluctantly performs an original song on the keyboard, and Phoenix is deeply affected by her voice and songwriting. He passes the English final and kisses Lennon in a moment of elation. They grow physically closer and eventually have sex for the first time. Phoenix discovers Lennon was a virgin, a fact she concealed, but tells her he wants to "pursue this."
Everything changes when Phoenix learns that Vic Doherty, a legendary record executive from Phantom Rock Records, will attend the band's upcoming show at Voodoo, a local venue. Phoenix and Storm have no original music, and Phoenix realizes Lennon's song is exactly what he needs. On the night of the show, Lennon arrives backstage to find Sabrina emerging from Phoenix's dressing room, with Phoenix zipping his pants. Devastated, Lennon tells him she never wants to see him again. Phoenix never responds to her texts.
Four months later, Lennon is at Dartmouth College when she hears Sharp Objects' debut single on the radio and recognizes her stolen lyrics. The narrative jumps four more years. Phoenix, now twenty-two, is a Grammy-winning rock star. The band has expanded to include Memphis, a guitarist, and Josh Roland, a bassist; all four members came from difficult backgrounds and were brought together by Vic. At a post-Grammy party, Josh tricks Phoenix into using heroin, then crashes a stolen car while driving intoxicated, killing himself, a pregnant woman, and her four-year-old son. Phoenix survives with severe injuries.
Consumed by guilt, Phoenix spirals into substance use and reckless behavior, burning through ten sober companions by seducing all of them. Josh's fiancée, Skylar, is hired as the band's new publicist. Storm suggests hiring Lennon as Phoenix's sober companion, reasoning she hates him enough not to sleep with him. Lennon's life has changed: Her father was diagnosed with early-onset dementia, forcing her to drop out of Dartmouth and tend bar to support them both. Encouraged by her neighbor Mrs. Palma, Lennon accepts and negotiates $350,000, payable only upon completing the full eight weeks, with one critical rule: no sexual relations with Phoenix.
Lennon arrives at Phoenix's hotel to find a debauched party. She clears the room and handcuffs him to the bed. The next morning, Phoenix recognizes her and is stunned by her transformation. Lennon tells him she is there to ruin him. He tries to have her fired, but Storm and the record label prevent it, and an uneasy truce is struck.
On tour, Phoenix refuses to sing "Sharp Objects" at concerts, unable to perform Lennon's stolen lyrics in front of her. George, the fill-in bassist, develops feelings for Lennon, provoking Phoenix's jealousy. Despite their hostility, Phoenix and Lennon begin a sexual relationship that Lennon insists is temporary, expiring at the end of the tour.
Quinn Moore, a fifteen-year-old, breaks into Phoenix's hotel room claiming to be his half-sister through their shared mother, Genevieve. Quinn reveals that her stepfather Chad, a sheriff, physically abuses both her and Genevieve. Phoenix orders a DNA test and keeps Quinn on tour. When Quinn disappears and returns badly beaten, Phoenix confronts Chad and extorts him into allowing Quinn to stay. The DNA test confirms she is his sister. Phoenix also confronts Genevieve, who admits that when she left Vance, Chad refused to accept Phoenix, so she abandoned her son. Phoenix offers to help Genevieve escape, but she refuses to leave Chad.
During a recreation of their old drinking game, Phoenix finally admits why he stole Lennon's song: His dyslexia prevents him from writing original material, and he needed something extraordinary to impress Vic. Lennon is crushed, telling him she would have given him the song willingly if he had asked.
In their final days together, Phoenix takes Lennon to The Dakota in New York City, the building where John Lennon lived and was killed, honoring her namesake. He then flies her to Los Angeles and recreates the setting from Storm's garage. Lennon discovers a stack of handwritten letters Phoenix wrote to her over the years but never mailed, revealing his remorse and awareness that his success was built on her gift.
Phoenix convinces Lennon to stay three more days for the European tour's opening concert at Wembley Stadium in London. He brings her on stage to sing "Sharp Objects" before ninety thousand people, and she delivers a stunning performance. Phoenix then addresses the crowd and publicly confesses that Lennon wrote the song and he stole it, sending the band into crisis. Backstage, Lennon receives a call: Her father has had a severe stroke.
Lennon rushes home to find Don on a ventilator with irreversible brain damage. Phoenix flies to her side. When Lennon says she is all alone, Phoenix proposes. She accepts, and a hospital chaplain marries them at Don's bedside. Seconds after they are pronounced husband and wife, Don passes away.
Lennon falls into deep grief, and Phoenix cancels the European tour to stay with her. Vic threatens to sue Phoenix and replace him, and Phoenix effectively walks away from his career. When Lennon learns the extent of the crisis, she devises a plan: She will publicly claim she cowrote the song and asked not to be credited because she feared comparison to her songwriter father. She warns Vic through Skylar that if he does not cooperate, she will sue him for every cent earned from her work.
Phoenix encourages Lennon to return to songwriting, placing her old journal on her father's piano and repeating Don's advice. Lennon sits at the piano and begins to play. In the epilogue, set three months later, Phoenix has returned to the studio. He arrives at a small bar where Lennon is performing her own original music, radiantly happy. She sings a new song incorporating words from his unsent letters. A fan recognizes Phoenix and remarks that he once "had it all" and "lost it." Phoenix watches his wife perform and silently disagrees.