Police Captain Jim Fitzpatrick (Walter Huston) is a dedicated family man and crime fighter not averse to using violence to fight violence. Although he's been demoted for political reasons, public outcry forces the mayor to take more aggressive action against sleazy gang boss Sam Belmonte (Jean Hersholt), and Fitzpatrick is promoted to police chief. His younger brother, Police Detective Ed Fitzpatrick (Wallace Ford), allows himself to be seduced by a languorously sexy Belmonte gang moll (Jean Harlow) and needs money to continue the relationship. Frustrated when his principled brother will not promote him, he betrays Jim's trust by conspiring with Belmonte's henchmen in a truck hijacking that results in the deaths of a child and another police officer. After a crooked lawyer is able to get those guilty off on all charges, the relentlessly determined Chief turns to vigilantism to rid the city of its "Beasts."