Diane Ford (Michelle Monaghan), a vivacious and successful independent truck driver, leads a carefree life of long-haul trucking, one night stands and all-night drinking until the evening her estranged 11-year-old son (Jimmy Bennett) shows up at her door.

Peter hasn't seen his mother since he was a baby and wants Diane as little as she wants him; but with his father Len (Benjamin Bratt) in the hospital, Diane and Peter are stuck with each other - at least for a while.

Burdened with this new responsibility and seeing the life of freedom she's fought for jeopardized, Diane steps reluctantly into her past and looks sidelong at a future that is not as simple or straightforward as she had once believed.