Eager to convince the skeptical press that the San Quentin Inmates' Welfare League is a safe and productive organization, Warden Kelly agrees to bring three model participants of the program to a press club luncheon in San Francisco. One of the participants, the brutal Nick Taylor, is actually using the League to advance his nefarious activities and plans to escape en route to the luncheon. Former convict Jim Noland, who is the founder of the San Quentin League, is also slated to attend the luncheon with his best friend, Broadway Johnson. Although Jim doubts his old enemy Taylor's rehabilitation, Kelly maintains his belief in the criminal. As Kelly, Jim, Taylor and Tommy North, a new "recruit" who has been tutored by Taylor, drive to the luncheon, they are ambushed by Steve Marlowe, a cohort of Taylor's. During the ensuing confrontation, Tommy and Kelly are shot, and Kelly's driver is stabbed to death by Taylor. Taylor makes his escape with Marlowe, leaving the wounded Tommy behind. As a result of the attack, the prison's board votes to suspend all League activities and privileges. Determined to help the League and the wounded Kelly, who was shot while protecting him, Jim vows to bring in Taylor himself. To that end, he uses his League connections in and out of prison to track Taylor, who has since committed two robberies and murdered several people. Jim's tips lead him to ex-convict Jeff Torrance and his girl friend Ruthie, who reveal that Taylor is hiding in Fresno. Following Jim to Fresno is Al Schaefer, a plainclothes detective and former adversary. In Fresno, Jim meets up with fellow Leaguer Carzoni, who gives him a gun for protection. Al tails Jim to a drugstore, where he frisks him and discovers the address of Taylor's hideout. Al then goes to the hideout, a tailor's shop, but loses Taylor and Marlowe when they escape through a back window. During the ensuing car chase, Al crashes his car and suffers fatal injuries. Because Al was following Jim, Jim is now wanted by the police. Nick, meanwhile, receives supplies from Jeff, whose betrayal Nick quickly deduces. At Marlowe's suggestion, Nick resists killing Jeff and heads for a remote gun club, which is accessible only by boat. While Nick and Marlowe take over the nearly deserted club, Jim cables Betty Richardson, his devoted fiancée, for help. Through a coded message, Jim asks Betty to visit Ruthie to find out Nick's whereabouts. Posing as Jeff's long-lost wife, Betty is able to extract enough information out of the bemused Ruthie to enable Jim to pinpoint Nick's location. After Jim sneaks up on Marlowe at the club and shoots him, he and Nick engage in a prolonged fight, which Jim eventually wins. Nick's apprehension leads to the vindication of both Jim and the League, and Jim happily marries Betty.
