This Gun for Hire.

Sadistic killer-for-hire Philip Raven becomes enraged when his latest job is paid off in marked bills. Vowing to track down his double-crossing boss, nightclub executive Gates, Raven sits beside Gates' lovely new employee, Ellen, on a train out of town. Although Ellen is engaged to marry the police lieutenant who's hunting down Raven, she decides to try and set the misguided hit man straight as he hides from the cops and plots his revenge.