Mercedes Ron's novel follows Kamila "Kami" Hamilton and the Di Bianco brothers, Taylor and Thiago, whose intertwined childhoods were shattered by a family scandal and a devastating accident. The story alternates among Kami's, Thiago's, and Taylor's perspectives as all three confront guilt, grief, and attraction eight years after the event that tore their families apart.
A prologue set eight years earlier establishes the trio's bond. Ten-and-a-half-year-old Kami sneaks out at midnight to meet her neighbors: Taylor, who is her age, and his twelve-year-old brother, Thiago. They break into a local chocolate shop's basement to steal candy, and before helping Kami escape through a window, Thiago demands a kiss. She complies, and they flee. The narrator describes this as Kami's first kiss and their last adventure together.
Eight years later, Kami is nearly eighteen and starting her senior year at Carsville High. Her mother, Anne Hamilton, is controlling and image-obsessed, while her father, Roger, a financial advisor, is kind but frequently absent for work. Her six-year-old brother, Cameron, is the bright spot in her life. On the first morning of school, Kami notices a moving truck at the Di Bianco house next door, which has stood empty since the families' falling-out. At school, she finds Taylor, but he is cold and distant, leaving her devastated. She is also dating Danny Walker, the mayor's son, in a relationship partly arranged by their families, though she is no longer in love with him.
Thiago, now twenty, narrates his bitterness toward Kami. He blames her for revealing, at age ten, that Anne was having an affair with his father, Travis Di Bianco, a revelation that led to his parents' divorce, his mother Katia's depression, and years of suffering. Since leaving Carsville, Thiago has dropped out of college and landed on probation for assaulting Katia's abusive boyfriend. A restraining order against the boyfriend forced the family back to Carsville. Thiago takes a job at Carsville High as an assistant basketball coach and detention supervisor, arranged by Principal Harrison, who warns him against forming relationships with students. When he and Kami collide in the hallway, he feels an unwanted attraction but coldly tells her to let go.
Danny pressures Kami physically in his car before a basketball game, and she breaks up with him. He becomes abusive, locking the doors, until Taylor knocks on the window and Kami escapes. At a party afterward, Kami challenges Taylor to a pool game in which the winner can ask the loser for anything. She wins and asks for Taylor's forgiveness. He tells her it was never her fault and embraces her. Thiago watches from across the room, visibly hostile. His internal conflict deepens as his feelings shift from hatred to attraction. The three argue outside about the past, and Thiago declares he hates the entire Hamilton family. Taylor drives Kami home, and they begin reconnecting.
The Hamilton household deteriorates. Roger reveals his company faces ruin because an employee has been embezzling. The family sells Kami's car and lets go of their longtime cook. When Kami confronts Anne about the Di Biancos, pointing out that Anne caused the families' problems, Anne slaps her.
Taylor and Kami are paired for a biology project, and their flirtation intensifies. At the Di Bianco home, Katia greets Kami warmly, and Taylor nearly kisses her before Katia interrupts. As Kami leaves, she impulsively kisses the corner of Taylor's lips, then runs into Thiago on the porch. Inside, Taylor declares he likes Kami and will invite her over whenever he wants. Katia tells Thiago she always knew one of her sons would fall for Kami. Thiago responds that he cannot share a roof with someone responsible for the death of the person he loved most, the first reference to his younger sister.
Danny's behavior turns dangerous. He ambushes Kami in the school parking lot while drunk, pinning her against her car and trying to force himself on her. Taylor and Julian Murphy, a classmate new to Carsville, intervene. In the principal's office, Kami lies to protect everyone, and she, Taylor, and Julian each receive two weeks of detention supervised by Thiago.
Taylor kisses Kami during a class film screening. They are caught and warned that further violations risk expulsion. During detention that evening, Thiago corners Kami and orders her to stay away from Taylor. When the lights go off, a charged, intimate encounter between them leaves both deeply shaken.
On an away trip to the rival town of Falls Church, a hungover teammate fails to catch Kami during a cheerleading routine, and she crashes headfirst onto the gym floor. Delirious, she tells Thiago she dreamed he was kissing her. She later quits the squad. Taylor comforts her, and in his motel room they begin making out, but Kami realizes she is imagining Thiago.
As the anniversary of a traumatic event approaches, extended flashbacks reveal the full story. Eight years earlier, young Kami and Thiago witnessed Anne and Travis together in the woods. Thiago made Kami promise not to tell. But after reading online about divorce and custody, Kami grew terrified that her mother would take her from her father and told Roger what she had seen. At the fourth birthday party of Lucy Di Bianco, Thiago and Taylor's younger sister, Roger found Anne and Travis together and attacked Travis. A violent brawl erupted in front of the guests and children. Katia grabbed her three children and drove away in hysterics. On the yellow bridge between Carsville and the neighboring town, Katia was driving nearly ninety miles per hour when a deer leaped into the road. The car struck the railing, flipped, and plunged into the lake. Thiago broke a window, freed his unconscious mother, and pulled Taylor from the submerged car, but four-year-old Lucy's seatbelt was jammed. Despite repeated dives, he could not free her. Lucy drowned. At the funeral, twelve-year-old Thiago shoved Kami and told her it was her fault. Taylor defended Kami, telling Thiago that he was the one who could not save Lucy, words that have haunted Thiago ever since.
On the anniversary, both Thiago and Kami are drawn separately to the bridge. He finds her biking in a dangerous storm and drives her toward home. Parked on the roadside, they have the honest conversation they have needed for eight years. Thiago admits he blamed Kami because it was easier than blaming himself for failing to save Lucy. Kami explains she told her father because she was terrified of losing him. They acknowledge the tragedy resulted from a chain of events no single person caused. Thiago asks if she ever liked him more than Taylor. She replies, "It was always you, Thiago. It always was, it is, and it always will be" (243). He kisses her passionately, but she whispers Taylor's name, breaking the spell. He frames the kiss as a peace offering rather than a beginning.
At home, the Di Bianco family enters Lucy's preserved bedroom, untouched for eight years. Katia sits on the floor clutching Lucy's pajamas. The brothers comfort her, and Thiago gently insists she must donate Lucy's belongings, as they agreed when they moved back. Katia asks for one more day, noting Lucy would have been turning twelve.
In a brief epilogue, the family donates Lucy's things and visits her grave. Thiago places a lollipop by the headstone, recalling how Lucy never listened when told to eat dinner first. He smooths out a crumpled drawing he took from Kami during detention: a portrait of all four of them from a childhood photo. Watching Kami walk next door to see Taylor, Thiago thinks he should tell her to wait for him. But he concedes that Taylor deserves her, that he has nothing to offer, and that he no longer has the strength to fight. He drives away.