Seventeen-year-old Olivia Hudson lives in the small town of St. Francisville, Louisiana, where she's lived her entire life. Her mother's suicide (committed by drowning on her own eighteenth birthday) seems to define her life: people avoid her like suicide is contagious, and she inadvertently mimics her mother in many of her actions and habits. Olivia lives alone with her grandmother, whose memory is deteriorating (calling Olivia "Lillian," her mother's name). Her father, who left her mother before she died, is too afraid and full of regret to adopt her. Olivia has three good friends: Jamie Benton, the boy she's grown up with and who deals with an abusive father; Max Barrow, her attractive but hotheaded sometimes-boyfriend; and Maggie Herrington, a short singer and aspiring artist whose fierce loyalty defines her.
Olivia is at Jamie's house, helping him and his mother fix dinner, when his father comes home early from work, drunk and angry. He goes off on his family members and acts horribly to all members involved, and Jamie finally snaps, attacking his father in a moment of rage. In the ensuing fight, Jamie stabs his father in the stomach with a kitchen knife, and Olivia hits him in the head with a skillet. Mr. Benton falls, hits his head on a corner, and falls unconscious, bleeding profusely from his stomach and head.
Olivia and Jamie run away, grabbing only the necessities and contacting Max and Maggie, who come in Max's truck and pick them up. The four of them go on the run, throwing away their phones and trying to put distance between themselves and the disaster. They decide to head to New Orleans, where Olivia's mother's best friend has just moved. Maggie's mom lives there as well, and she thinks her mother has a friend who would let them crash at his place.
On the road, the four protagonists have a couple of close calls, but they make it to New Orleans. The four of them locate the house of Maggie's mom's friend, Steven, who allows them to stay at his place (which seems to be a hub for drug addicts and street dwellers). While staying at Steven's, they find out that the police are after them, so they have to keep a low profile. Maggie gets together with her mother, an aspiring singer, who seems to be working more on developing her drug addiction than her singing career. Their reunion is brief and stormy, as Vicky (Maggie's mother) attempts a drug deal in the same house and at the same time as she meets Maggie. Maggie tests her by asking the dealer to inject her, and Vicky fails, doing nothing to stop him. Maggie explodes in a rage, and the reunion is over.
Later, at a live music bar, Maggie sings, wowing the crowd, before asking her mother for her contact that can sell them fake IDs. Olivia gets drunk and starts dancing on a table, causing Max to start a fight with a guy who grabs her leg. In the fallout, they regroup at Steven's house, dejected. Olivia makes contact with Beth, her mother's old friend, who will give them five thousand dollars in memory of Lillian. Using this money, the friends plan to buy fake IDs and passports from Vicky's contact for Olivia and Maggie, and then Max and Maggie will turn themselves in.
On the way to the meeting, however, Vicky sorrowfully reveals that she sold them out in order to pay off her debt to Louis, the passport guy. In the ensuing chaos, Mark, the drug dealer who almost injected Maggie earlier, draws a knife on Olivia and Jamie in an alleyway. He decides to take the five thousand dollars they're carrying instead of turning them into the police, but he attempts a parting slice at Olivia, and Jamie gets in the way. The knife rips open his abdomen, and Jamie bleeds out on the sidewalk as the police arrest Mark and stop the frenzied action.
After Jamie's death, Olivia grows cold and hollow, and she seems to be losing ground in her struggle against the pull of mental illness. Before Max and Maggie leave for college, they have one last meaningful night lying in the graveyard, where both Jamie and Lillian are buried. In the morning, they leave, and Olivia's father takes her to his new house, where he has made a room for her. In the end, Olivia plans to go off to a tiny liberal arts college in the mountains, close enough to Max and far from any bodies of water. Olivia also starts seeing a psychiatrist, who advises her to speak to her mother at her grave, which is how the novel concludes.
