Trucker is being sold primarily on the merits of its lead performance, a stripped-down turn for Michelle Monaghan, an actress who has been ubiquitous in a series of almost-good Hollywood movies but hasn't really had a chance to show her stuff. On that central promise, the movie pretty much delivers-- Monaghan is brave and moving as Diane, a hard-living truck driver forced to face responsibility for the first time when she must care for her 11-year-old son Peter (Jimmy Bennett).
Based out of California, Diane returns to an empty house between trips for visits to the VFW bar with Runner (Nathan Fillion), a neighbor who's chastely in love with her, and pretty much nothing else. She hasn't had contact with her son or her ex in year when her ex's new wife (Joey Lauren Adams) shows up with Peter in tow, saying Diane's ex-husband (Benjamin Bratt) has gotten sick and there's no one else to care for the kid. Diane clearly has no idea what she's doing-- she throws the kid a blanket on the couch and leaves him there, and seems shocked to find him there in the morning--but takes Peter with her on the road for her next job anyway. The two don't immediately bond on the road-- that would be too easy, even for this film-- but the mother-son intimacy does start up thanks to a series of mostly unbelievable set pieces, from Diane sticking up for Peter against bullies to a whipped cream fight at home.
The biggest problem isn't really the action, but the terrible, faux hard-boiled dialogue the actors are hampered with. Monaghan, for all the physical ways in which she manifests Diane's tough attitude, seems uncomfortable spouting off the curse words assigned to her, whereas Bennett sounds more like a foul-mouthed truck driver than she does. As a result Monaghan's performance, the film's biggest strength, is hampered; she has to be fully believable for the thing to work, and the tin-eared dialogue always keeps her a step removed from perfect.
At their best, movies like Trucker allow us access to a previously forbidden world, revealing the chatter at the truck stops and the story behind that woman too pretty to be wasting her time at the VFW. But Trucker is too caught up in its explicit emotions, the mother and child reunion and the ability for Diane to accept love in her life, that it misses the smaller details that would have made it complete. Mottern leaves plenty of room for Monaghan and her performance to wow us, but doesn't provide enough framework around her to sell it in the end.