Mercer White, a 19-year-old with a restless impulse, steals a Volvo station wagon from a car wash in Eugene, Oregon and sets off to locate his estranged half-brother, Arlen, who does not know that their mother has recently died. Soon after he leaves, a cell phone in the car starts ringing, and Mercer speaks with the car’s owner, Kate, who lends him her vehicle on one condition: he must call regularly to describe his journey.
Mercer heads to Shelter Cove, California, a bohemian pottery community where Arlen once lived, only to discover that his brother has moved on to Reno, Nevada. His route takes him through Fallon, Nevada, where he encounters his middle school crush, Joely. In Reno, they share a night of ecstasy and flirtation, but Mercer stays focused on continuing his search for Arlen. His path then leads him to the set of a pornographic film, where the director informs him that Arlen left that life to work at a pet store in Sacramento, California. Along the way, Joely asks Mercer to drive her cousin Buddy and his friend Rid to Mojave, California, where they are attempting to build their own car.
During the drive, Mercer discovers Kate’s YMCA card tucked in the trunk of her car. With this realization, he envisions a dream where he, Joely and Kate dance together in a re-enactment of Bande à Part’s famous sequence. He tries to move on without being pulled off course, but when Buddy threatens to steal the car, Mercer asserts that the car belongs to his girlfriend, and Buddy, Rid, and Joely depart. Mercer then hitchhikes to Mojave and locates the salvage yard where Buddy and Rid work, reclaiming the car.
Back in the car, Mercer speaks to Kate while driving and imagines her sitting in the back seat; she grows jealous when he mentions Joely, and she eventually ends the call. He reaches Sacramento and finds the pet store where Arlen once worked. The store owner asks Mercer to sing in a children’s band as part of a probation agreement. When he returns to the car, he finds someone attempting to break in; it turns out to be Kate. They spend the night in a hotel, but Mercer leaves the next morning and catches a train to Los Angeles. With the help of a translator, he calls Arlen’s last known residence and learns from a Hispanic woman that Arlen is working at a hotel in Ensenada, Mexico.
Mercer eventually meets Arlen at the Ensenada hotel, but Arlen assumes Mercer is after money. In a brief confrontation, Mercer tackles his brother to the ground and is kicked out. Later, Kate finds a bloodied Mercer by the side of the road and drives him to a hotel. She confesses that she let him take her car because she was attracted to him, and the two share a night of intimacy. The following day, Mercer encounters Arlen again, and the two part more amicably after Mercer explains that he and Kate are planning to drive to Louisiana to spread their mother’s ashes.
