It is during the great depression in the US, and the land is full of people who are now homeless. Those people, commonly called "hobos", are truly hated by Shack (Borgnine), a sadistical railway conductor who swore that no hobo will ride his train for free. Well, no-one but "A" Number One (Lee Marvin), who is ready to put his life at stake to become a local legend - as the first person who survived the trip on Shack's notorious train.