这部由三大艾美奖获奖演员John Wells、Ann Biderman和Chris Chulack联袂主演的罪案剧，以独特的视角讲述了发生在洛杉矶警察局的警察故事。从风光秀丽的马利布（Malibu）海滩，到错综复杂的东洛杉矶街道，到处都活跃着他们的身影－－他们要与犯罪分子作斗争，要与受害人打交道，还要求得家人的理解和支持。　　Michael Cudlitz（A River Runs Through It）扮演经验丰富的资深警察John Cooper，奉命指导警队新秀Ben Sherman（Benjamin McKenzie, The O.C.）。Cooper忠诚、严肃、务实、做事必求结果的工作态度，让浮躁的Sherman怀疑自己是否能当一名合格的警察。　　女警探Lydia Adams（Regina King，Ray, Jerry Maguire）与母亲同住，照顾母亲是她现在的首要任务。她的搭挡Russell Clarke（Tom Everett Scott, Boiler Room）是个婚姻不幸的男人，家里还养着三个孩子。Daniel Sal Salinger警探（Michael McGrady, The Thin Red Line）是刑事侦探组的小头目，Nate Moretta警探（Kevin Alejandro, Drive, Ugly Betty）和Sammy Bryant（Shawn Hatosy, Alpha Dog）警探都听从他的指挥。巡警 Chickie Brown（Arija Bareikis, Crossing Jordan）是个单身母亲，梦想着有朝一日能成为特种武器和战术部队（SWAT）的第一位女性成员。

Officer John Cooper returns to duty after recovering from back surgery and meets his new partner, Officer Jessica Tang, a tough and disciplined cop with her own set of baggage from working the streets. Lydia, whose new partner is Ruben Robinson, can't seem to escape helping a former CI who won't stay in safety. Ben, Sammy and Dewey chase an armed man into an elementary school, while Ben bumps heads with an intense street cop whose cynical attitude is affecting their work.

Ben Sherman is about to complete Phase 2 of his rookie year. During Phase 3, he will be allowed to patrol solo. Detective Adams and Officer Brown are assigned new partners. Rene Cordero, Adams's new partner, is obsessed with receiving glory and press coverage. Their first case involves the search for an elderly man who left his home accompanied by an unknown black man. Brown's new partner, Slug Ferguson, quickly demonstrates how he earned that nickname when he starts a riot during a traffic stop. Meanwhile, Detectives Moretta and Bryant investigate a Sonora shootout involving a young Mexican man shot dead while driving an unregistered Bentley.