On the way to meet his former boss, railroad tycoon Ben Kimball (Jay C. Flippen), Grant McLaine (Stewart) rescues a young boy, Joey Adams (Brandon deWilde), from Concho (Robert J. Wilke). Ben informs Grant that his payroll has been robbed three times already by a gang led by Whitey Harbin (Dan Duryea) and the Utica Kid (Murphy). If Ben's workers don't get paid soon, they will all leave the end-of-track work camp. Grant accepts the undercover job of carrying $10,000 to the crew by train.