Fifteen-year-old Callie sits across from her therapist at Sea Pines, a residential treatment facility, and refuses to speak. Asked if she remembers how the cutting started, Callie remembers exactly. At her last cross-country meet, she fell behind every runner until the final girl ahead disappeared. Callie felt a spike of fear: If she could not see the other girl, no one could see her. She ran home and found an Exacto knife on the kitchen table. She pressed the blade to her palm, felt satisfied and released, then exhausted. She tells the therapist none of this.
Her roommate, Sydney, who has a drug addiction, nicknames her S.T. for Silent Treatment. The facility, which the girls call Sick Minds, labels its patients "guests" and its nurses "attendants." Callie's therapy group includes Tara, who hides a bald spot under a baseball cap; Becca, who arrived after a heart attack; Debbie, who has been at the facility the longest; and Tiffany. In Group therapy, led by a counselor named Claire, Callie sits apart from everyone. As a Level One patient, the lowest behavioral tier, she cannot go anywhere unsupervised. Ruth, a shy patient, escorts Callie to therapy each day. At night, an attendant named Ruby talks for both of them and slips her butterscotch candies.
The therapist waits session after session. Callie never speaks, but internally she replays visiting day. Her eight-year-old brother Sam, who has severe asthma, gave her a card signed by Sam and their cat, Linus. Their mother whispered that insurance refused to cover treatment because cutting is considered self-inflicted. Callie dissociated and rubbed her wrist along a restroom paper towel dispenser until she bled. She found Sam alone in the game room, where he spoke for both of them, asking when she was coming home. Their father did not attend.
The therapist suggests Callie's silence is her way of asserting control. One evening in the game room, the therapist drops a red checker into Callie's Connect Four board, completing a diagonal row of four, rests her hand on Callie's shoulder, and leaves. A new girl, Amanda, soon joins the group. When Amanda removes her sweatshirt, the group gasps: Her inner arms are covered with geometric scars, and the words "Life" (36) and "Sucks" (36) are scratched into her skin. Amanda insists cutting is body decoration she can control. Claire asks Callie directly if Callie can control it, exposing her secret to the group. That night, Sydney whispers across the gap between their beds, asking Callie not to hurt herself.
Ruth graduates and leaves. The therapist ends a session early, telling Callie that watching her count wallpaper stripes is not helping. Callie's mother calls to say staff may send Callie home because they view her silence as resistance to treatment; Callie cannot return to school without completing treatment either. That night, she tears a hidden aluminum pie plate in half and presses a jagged edge into her wrist. This time there is no relief, only pain. For the first time, she tries to stop the bleeding. She holds out her arm at Ruby's desk. Ruby bandages the wound and presses both hands around Callie's wrist until the bleeding stops. Callie surrenders the pieces.
Before dawn, Callie goes to the therapist's office and waits in the dark hallway. When the therapist arrives, Callie manages: "I can't" (54). Then: "Talk" (55). She cries for the first time. The therapist promises that Callie will find something better to replace whatever she gives up. Callie agrees to try.
Callie begins describing Sam's asthma, her mother's anxiety, and how the household revolves around Sam's illness. She assumes heavy cleaning duties and never acknowledges her own exhaustion. When the therapist asks if Callie feels her mother does not want her around, Callie realizes she has said something not quite true, or perhaps a little bit true. In Study Hall, when Sydney thanks her for passing a note, Callie replies "Sure" (85), the word escaping without effort.
Callie tells the therapist about assembling Sam's tabletop hockey game while her parents were out. She yelled at Sam for putting stickers on crooked; he started crying and could not breathe. In a memory she does not share, Callie ran to Bud's Tavern, where she found her father drinking. Her parents rushed Sam to the hospital; returning after midnight, her mother knelt crying, saying Sam almost died. After that night, her mother stopped driving. Callie withholds the detail of her father's location. The therapist assures Callie she is not crazy: Callie has developed a way to deal with overwhelming feelings, and the therapist can help her stop if she wants to.
Becca is found in the infirmary with an irregular heartbeat from dehydration caused by vomiting. When Debbie confesses in Group that she blames herself, Callie speaks for the first time: "It's not your fault" (101). She confesses she witnessed Becca hiding food and vomiting but said nothing. Sydney tells Callie it is not her fault either. Callie breaks down sobbing. Afterward, she joins the girls on the smoking porch.
Callie tells the therapist she believes everything is her fault: Sam's illness, her mother's deterioration, her father's absence. The therapist explains that asthma is an allergic reaction no one can cause by upsetting someone, and asks whether Callie is punishing herself. Callie says she feels like a bad person but does not know what she has done that is so bad, and she recognizes this as the truest thing she has ever said.
Becca returns to Group in a wheelchair. Tara tells Becca her actions hurt everyone, including Callie for the first time. Debbie checks on Callie, then catches herself in her pattern of caring for everyone else. Callie is upgraded to Level Two, which grants her more independence. Tiffany departs when her insurance runs out, revealing that the purse she always carried held her old baby blanket. Amanda reveals a staple hidden under a Study Hall chair and asks what tools Callie uses to cut. In therapy, Callie shows the therapist her scars and surrenders a metal strip she had been keeping. The therapist tells Callie she cannot keep Callie safe; only Callie can.
The therapist revisits the night of Sam's attack. Callie recalls that Sam had an infection and a doctor had advised monitoring him, yet both parents went out, leaving her alone with a sick child. In Study Hall, Callie thinks about Amanda's staple, spirals into worry, and decides she knows exactly what to do.
Callie pushes open an unlocked exit door and runs until she reaches a pay phone. She calls her father at work. At a nearby Dunkin' Donuts, a waitress recognizes her as a runaway and gives her hot chocolate. Her father arrives and hugs her. Callie tells him she thought Sam's illness was her fault. Her father says he was supposed to be watching Sam and refuses her reassurances.
When her father asks where they are going, Callie pictures home: her mother, Sam, Linus the cat. Then she pictures Sydney, Tara, the circle of feet in Group, Ruby's white shoes, the therapist's fabric shoes. She chooses to go back. Her father reveals during the drive that Callie's mother drove to visiting day, a feat for a woman who had stopped driving. He says he and Callie's mother are trying harder, and he apologizes for never visiting. At Sea Pines, Callie declares she wants to get better. Her father fights tears; Callie smiles at him because she knows this is not something to cry about. She plans to share doughnuts with the girls and tell the therapist everything in the morning.