Framed for the murder of a policeman, gangster Joe Blake commits suicide. "The Bat," a gang leader, is the real murderer. Joe's twin brother, Ralph, joins the gang to get revenge and clear Joe's name. There he meets the daughter of the murdered policeman, Isobel, posing as "State Street Sadie" to get her own revenge. The two become involved in a net of intrigue culminating in the capture of the gang by police. The Bat, trapped on a roof, leaps to his death while Ralph and Isobel contemplate marriage.