It's 1949 Los Angeles| and gangster Mickey Cohen has moved in| with the intention of controlling all criminal activity in the city. He has bought local judges and police| and no one is willing to cross him or testify against him. Everyone except Seargant John O'Mara| a former World War II soldier| whose goal is to settle with his family in a peaceful Los Angeles. Police Chief William Parker decides to form a special unit whose mission is to take down Cohen| and chooses O'Mara to lead the unit. O'Mara chooses 4 cops and asks another cop and vet| Jerry Wooters to join him but Wooters is not interested. But when he witnesses the murder of a young boy by Cohen's people| he joins them| and they decide to take apart Cohen's organization. Cohen wonders if a rival is going after him| but eventually he realizes it's the cops.
Though it's stylish and features a talented cast, Gangster Squad suffers from lackluster writing, underdeveloped characters, and an excessive amount of violence.