Unhinged

In a stormy 4:00 AM morning, Tom Cooper sits in his pickup outside a house, takes his meds, and approaches with a hammer. He smashes the door, confronts the couple inside, and kills them before setting the house on fire.

Rachel Flynn, a divorced mom, lives with her son Kyle along with her brother Fred and Fred's girlfriend Mary. She receives a call from Andy, her lawyer and friend, who informs her that ex-husband Richard wants to claim their house. The threat of losing their home hangs over her family as the day begins.

Rachel drives Kyle to school while they navigate heavy traffic and the looming fight over the house. Kyle speaks with Richard, who says he can't attend Kyle's upcoming game, highlighting the strain between them. Later, Rachel tells a client, Deborah Haskell, that she is running late, and Deborah fires her out of frustration.

At a red light, Cooper stalls behind Rachel's car and ignores the signal to move. The light changes and Cooper continues to threaten her as they drive, cutting off her progress. Rachel honks in frustration and tries to pass, but the danger persists.

After stopping at a gas station, Rachel notices Cooper's truck behind her. Leo volunteers to help by taunting Cooper to get a license plate, but Cooper rams Leo with his truck, killing him. Rachel speeds away as Cooper pursues, intensifying the chase.

Cooper tracks Rachel to a diner and confronts her there, posing as a friend. When Andy intervenes, Cooper smashes a mug and slams his head down before stabbing him to death with a butter knife in front of horrified patrons. He leaves the diner still threatening Rachel.

To terrify Rachel further, Cooper keeps her on the phone and forces her to decide who will die next or reveal Kyle's location. She suggests Deborah Haskell as payback for firing her and uses the plan to lure him toward Deborah's house, hoping to trap him with police attention.

Cooper arrives at Rachel's house with Mary, while Fred watches the news of the diner murder. He tears through the home, Mary is killed in the assault, and Fred is restrained as Rachel races to Kyle's school to retrieve him.

Responding officers storm the attack at Rachel's house and shoot Cooper in the shoulder as he tries to escape. The immediate threat is interrupted, and the fire is put out as responders deal with the aftermath and free Fred from danger.

Cooper steals a minivan and pursues Rachel and Kyle on the highway, rear-ending a police officer and triggering a massive pile-up. A nearby driver watching the chaos crashes into a guardrail, escalating the carnage as Rachel fights to reach safety.

Rachel drives to her mother’s old house and hides Kyle inside, waiting for Cooper. She drives her car into Cooper's vehicle to flip it, knocks him to the ground, and the struggle ends with Rachel stabbing him in the eye with scissors as she fights to kill him.

Police arrive and take Rachel's statement, while officers reveal that Fred is alive and can be visited in the hospital. On the way to see him, a driver cuts Rachel off at a green light, and Kyle tells her she made a good choice by fighting back and surviving.