It's the cold heart of The Great Depression. Driven by hardship and poverty, Bucky Ellis hops his first freight train at the tender age of thirteen. Leaving home is the hardest thing he's ever done, but, as the oldest of the five Ellis children, he knows the family will be better off with one less mouth to feed. Luckily, he finds a new friend and mentor in that first boxcar he climbs into. K. O., son of a black prizefighter, teaches Bucky how to fight, and he teaches him the "rules" for staying alive. Together, the boys begin their search for a better life.

As the two friends ride the rails, there are a quarter-million others just like them--all in search of work, of something better. Bucky quickly discovers this is a new world with its own rules--where the kindness of strangers has to be depended on, and where that kindness is more than overshadowed by the brutality of the railroad detectives, or "bulls". As if life wasn't hard enough, when Bucky disfigures Crusher, one of the worst of these railroad detectives in a struggle that saves K.O.'s life, the boys make a deadly enemy.

As Bucky grabs opportunities and begins his assent to a better life, Crusher is waiting, watching. Brilliant, psychopathic, patient, the bull is determined to see Bucky dead--after the kid pays in pain.