Following the tragic loss of his mother in a car accident, T.J. (Devin Brochu) struggles deeply with his grief and slips into a profound depression. He becomes fixated on the vehicle involved in the fatal crash and decides to follow it when it is towed away. Living with his passive and pill-popping father, Paul, and his grandmother, Madeleine, T.J.'s life takes an unexpected turn when a squatter named Hesher (Joseph Gordon-Levitt), who is foul-mouthed, tattooed, and has a penchant for heavy metal music, crashes into their lives.
As T.J. navigates life at school, he encounters a bully named Dustin, who works for the towing service. After Dustin vandalizes his car and unfairly accuses him of the crime, T.J. finds unexpected support from Nicole (Natalie Portman), a grocery store clerk who helps him when he is attacked. However, Hesher, a confusing figure in T.J.'s life, witnesses the altercation but remains apathetic. Later on, in a bizarre twist of fate, Hesher retaliates by setting Dustin's car on fire, leading the police to question T.J. about the incident, but they have no solid evidence to charge him.
Determined to escape his overwhelming sadness, T.J. becomes obsessed with Nicole. One day, after an accidental encounter, Hesher takes both T.J. and Nicole to a random house, where chaos ensues as he vandalizes the swimming pool and leaves the two alone. This reckless behavior only adds to T.J.'s woes, particularly when he returns to find Nicole's car ticketed, prompting her to break down and lament her current circumstances.
Things at home grow tense when T.J. and Paul argue during dinner, leaving Madeleine in despair. The following morning brings yet another gut-wrenching blow as T.J. discovers that his grandmother has succumbed to her own suffering. In an impulsive act of desperation to reclaim his mother’s car, T.J. steals his father's credit card but learns that the vehicle has already been sent for crushing. In a fit of anger upon discovering that Nicole and Hesher are together, he confronts them, which leads him to damage Hesher's van as he declares his desire to distance himself from both.
As T.J. grapples with his emotions, he confronts Dustin at his house but is soon rescued by Hesher, who has been shadowing him. Despite this, T.J. informs Hesher that he no longer wishes to see him. Later, he sneaks into the junkyard and falls asleep in the wrecked car, haunted by dreams of his mother's last moments. He awakens just before the car is about to be crushed, narrowly escaping before witnessing its destruction.
The next day, while preparing for his grandmother's funeral, Nicole approaches T.J. seeking forgiveness but leaves without resolution. At the funeral, T.J.'s inability to speak leaves him feeling even more isolated. Then, Hesher barges in, intoxicated, and demands the attention of the mourners. He shares a bizarre yet poignant story from his past, emphasizing that even in loss, they still have each other—their shared experiences connecting them through grief.
T.J. and Paul, moved by Hesher's unexpected words, join him in carrying Madeleine's casket to the cemetery, creating a moment of camaraderie in their sorrow. The following day, Paul faces his own struggles and makes a significant change; he shaves for the first time in weeks. In a surprising gesture, he reveals that Hesher has retrieved the compacted remains of T.J.'s mother’s car from the junkyard and left it in their driveway with the bold proclamation, "Hesher was here." This act, while unconventional, serves as a reminder of their shared journey through pain and the beginning of potential healing.
