After undervalued supporting turns in Kiss Kiss Bang Bang, North Country, and Gone Baby Gone, dainty girl-next-door type Michelle Monaghan finally, and deservedly, snags a star vehicle to show off her chops. Against the roadside Americana of writer-director James Mottern’s well-shot desert drama, Monaghan flips the bird to vanity as a hard-drinking, promiscuous, blithe, and ballsy big-rig driver named Diane, and her performance is transformative enough to forgive Mottern’s boilerplate narrative. It’s the negligent parent and estranged child forced-reunion tale: Diane’s long-hauler lifestyle is literally slowed down when her angry 11-year-old son, Peter (Jimmy Bennett), gets dumped in her lap after baby-daddy Len (Benjamin Bratt) is hospitalized with cancer. There may as well be a road sign announcing Diane’s transformation from reckless loner to diligent mother, but it’s a smooth ride thanks to Monaghan, and an impressive ensemble. Bennett, last seen in Shorts, proves one of the more talented, least cloyingly precocious child actors today, and the always-charming Nathan Fillion continues his run as a married local who can barely suppress his feelings for bar buddy Diane.