A legendary hobo, A No.1 (Lee Marvin) is renowned for his expertise in riding the rails for free, but he meets his match with Shack (Ernest Borgnine), a fierce railroad conductor who mercilessly kicks stowaways off of his train. Joined by brash young hobo Cigaret (Keith Carradine), A No.1 manages to elude Shack but issues a challenge to the heavily armed conductor, announcing that he will ride the train for its entire route, leading to a violent showdown between the two strong-willed men.