Los Angeles, 1949.

Ruthless mob king Mickey Cohen (Sean Penn) runs the show in this town, reaping the ill-gotten gains from the drugs, the guns, the prostitutes and—if he has his way—every wire bet placed west of Chicago. And he does it all with the help of the police and the politicians under his control. That is, until, a small, secret crew of LAPD outsiders led by Sgt. John O’Mara (Josh Brolin) and Jerry Wooters (Ryan Gosling), come together to try to tear Cohen’s world apart.