After Hazel turns 18, Dee's ex-husband threatens to cut off child support unless Hazel agrees to treatment for her crippling agoraphobia. The pressure mounts to move Hazel toward a treatment center, so they embark on a van ride that Hazel finds daunting from the start. The journey is tense, with the two women clashing over Dee’s hard-living lifestyle and Hazel’s own neuroses, yet Hazel is reassured when her mother offers to accompany her. To accommodate Hazel’s fears, the treatment center allows her to travel in a box—a self-contained space that lets her isolate herself from others and the outside world.
In a brutal twist of fate, as they traverse the desert, half-brothers Pru and Jesse hijack the van to snatch a wealthy heiress. Pru, scarred by a traumatic head injury inflicted by an abusive mother, acts erratically and shoots Dee. Jesse finishes the violence by shooting everyone else in the van except the heiress and Hazel, who remain hidden inside the protective box. After the men depart, Hazel discovers her mother is wounded but still alive. A map points toward a nearby reservation, and Hazel tends to Dee’s wounds before deciding to head there for help. Dee, in a moment of heartbreak, finds a note Hazel has left behind detailing the reasons Hazel feels her mother has hated her.
Hazel continues her desert trek in a methodical, almost meditative way, focusing on small milestones—getting from one cactus to the next becomes a coping strategy. The dusty winds disrupt her pill-taking ritual, forcing her to discard some pills when they become too dirty to ingest. Along the way, she hallucinates the ghost of her dead sister, a figure from a drowning accident Hazel couldn’t prevent. Meanwhile, Jesse learns from an insider that one patient is agoraphobic, leading him to doubt that Dee was ever the patient in question. When he and Pru return to the van, they find Hazel’s box empty, and Jesse sets out to search for her. Dee, meanwhile, finds a pistol in the van and takes Pru hostage.
Across the desert, Hazel encounters a junkie named Clete who quotes Aldous Huxley. She manages to persuade him to help, but his promised motorcycle turns out to be nothing more than a disassembled wreck. Despair and distrust creep in as Clete’s ramblings about women intrude on her focus. She sprays him with pepper spray after he grabs it from her, and in the ensuing scuffle, she trips on a rock, hits her head, and loses consciousness. When she wakes, a kind couple has found her just outside the reservation and helps her get to safety. They contact the police and offer to drive Hazel back to her mother.
During the ride, the couple meets a representative from the treatment center who says he was dispatched to locate the missing van. He urges Hazel to let him pick up her mother and bring them to the treatment center. The couple, determined to protect Hazel, follow behind with rifles in tow. They all converge on Dee’s location at roughly the same moment, where she remains stubbornly holding Pru at gunpoint. Jesse, revealed to be the local sheriff, tries to take control, but Dee warns everyone not to trust him. The representative makes a move to intervene, but the determined couple open fire, killing the representative, Jesse, and Pru. In the end, Hazel rescues the kidnapped heiress and shares a tearful reconciliation with her mother.
