布里克(詹姆斯·卡格尼 James Cagney 饰)是一位非常具有正义感的律师,他的好友在不久之前遭遇了黑帮毒手,不幸身亡。这件事情深深的撼动了布里克,他决定放弃律师身份,加入美国司法部和联邦调查局,成为代号为“G”的特工。 在经历了一连串严苛的训练后,布里克被分配到了芝加哥办公,这是众所周知的罪恶都市,暴徒伤人抢劫的案件屡屡发生。布里克上任之后,暴徒一个又一个的被捉拿归案,黑恶势力遭到了极大的打击。在这个节骨眼上,布里克被挖出,曾经接受过黑帮的资金援助,这让他失去了上级的信任。与此同时,为了打击报复,黑帮绑架了布里克的女友(玛格丽特·琳赛 Margaret Lindsay 饰)。It's the early days of the F.B.I. - federal agents working for the Department of Justice. Though they've got limited powers - they don't carry weapons and have to get local police approval for arrests - that doesn't stop fresh Law School grad Eddie Buchanan from joining up, and he encourages his former roommate James "Brick" Davis (James Cagney) to do so as well. But Davis wants to be an honest lawyer, not a shyster, despite his ties to mobster boss McKay, and he's intent on doing so, until Buchanan is gunned down trying to arrest career criminal Danny Leggett. Davis soon joins the "G-Men" as they hunt down Leggett (soon-to-be Public Enemy Number One) and his cronies Collins and Durfee, who are engaged in a crime and murder spree from New York to the midwest.