Dick Manning, an assistant district attorney, who is on the track of a gang of murderers, is abducted while visiting his sweetheart, Helen Grant. Helen's police dog tracks down the abductors, and Helen goes to their den, passing herself off as Chicago Ann, a notorious female gangster who dresses in men's clothing. The leader of the gang is attracted to Helen, but his jealous sweetheart exposes her as a fraud. Helen is made prisoner, but she manages to escape with the help of a friendly gangster. Helen alerts the police, and the den is raided in time to save Dick's life.