Billy Byrne is a low class American born in Chicago's ghetto. He grows up a thief and a mugger. "Billy was a mucker, a hoodlum, a gangster, a thug, a tough." He is not chivalrous nor kind, and has only meager ethics - never giving evidence against a friend or leaving someone behind. He chooses a life of robbery and violence, disrespecting those who work for a living. He has a deep hatred for wealthy society.
He trains as a prizefighter but cannot stop drinking. When falsely accused of murder, he flees to San Francisco and is shanghaied aboard a ship. Enforced sobriety, brutal ship's discipline and productive work improves him. The ship's secret mission is soon enacted - the hijacking of a specific yacht to take a millionaire's daughter, Barbara Harding, for ransom. Billy Byrne brutally beats her suitor, Billy Mallory, leaving him for dead.