The telephone technician Mal Granger is a gambler and bon vivant. One day, his bookie and friend Chippie Evans introduces him to the crime boss Vince Walters and Granger proposes to expand his illegal bookmaking and gambling business using his technical knowledge of communication. Walters becomes a success and Granger forces him to make him his partner with 20% share. When Walters is killed by a bookie that commits suicide later, Granger becomes the owner of his business. Soon his business attracts the attention of the mafia and the powerful boss Carl Stephans proposes Granger to join his syndicate, with 50% of the profits. Granger accepts the deal and the bookies that do not accept the 20% fees for protection imposed by the syndicate suffer retaliation. The mobster Larry Mason is assigned by the syndicate to work in California with Granger and brings his seductive wife Gail Mason. Granger and Gail fall in love with each other and have a love affair. Granger's accountant Trudy Maxwell finds that Granger has been lured by the syndicate and he complains with Stephans that tells that there are additional costs in his shares. When Larry beats Gail, Granger hires the hitman Gizzi to kill Larry. Meanwhile, the honest Lt. Pete Wright from the Gangster Squad is investigating Granger, in the beginning of his downfall.