Years after escaping the clutches of his alcoholic father, cabdriver Carter (Adam Rothenberg) hears that Ellis (Ethan Peck), the brother he has raised as a son, has leukemia. In desperate need of a suitable bone-marrow donor, Carter and Ellis set off on a solemn drive from New Mexico to Knoxville, Tenn., in hopes of finding their errant father. Along the way, the two befriend truck-stop waitress Krystal (Mariah Carey), who joins them on the road -- with her own dark past in hot pursuit.