Doc McCoy is put in prison because his partners chickened out and flew off without him after exchanging a prisoner with a lot of money. Doc knows Jack Benyon, a rich "business"-man, is up to something big, so he tells his wife (Carol McCoy) to tell him that he's for sale if Benyon can get him out of prison. Benyon pulls some strings and Doc McCoy is released again. Unfortunately he has to cooperate with the same person that got him to prison.
The four Newton brothers are a poor farmer family in the 1920s. One day, the oldest of them, Willis, realizes that there's no future in the fields and offers his brothers to become bank robbers. Soon the family agrees. They become very famous robbers and execute the greatest train robbery in American history five years later.