When Frank Halloway breaks out of prison, his crooked lawyer arranges for him to follow the underground railway to Los Angeles where he hopes to collect his $250,000 share of the loot from his last job. The so-called railway is a safe route to Los Angeles with help from reliable criminal associates along the way. To help him along the way, the lawyer arranges for Mona Valentine to travel with him and pose as his wife. She does so for the money she's offered, even though she is repulsed by Halloway who is quite ugly. Along the way, however, he undergoes plastic surgery to the point that it creates a problem for him at the end of his journey. For Eliot Ness and the Untouchables, capturing Halloway is personal: Halloway killed a fellow agent.