 Cosmo Jones, a correspondence-school detective from a small town, comes to the big city to offer his services to the police. He happens by where a gangster is killed by an opposing gang. Socialite Phyllis Blake (Gwen Kenyon) is running around with gang member Tom (Gil Stanley) and the opposing gang plan on kidnapping her. Cosmo is with Sergeant Flanagan (Richard Cromwell) when the attempt is made in front of a night club, where a bystander is seriously wounded in the gun-battle. Police Chief Murphy (Edgar Kennedy) blames Flanagan for the shooting and demotes him. Cosmo, with the aid of a porter, Eustace (Mantan Moreland) and Flanagan s fiancee, Susan (Gale Storm), tries to find the killer. Phyllis is finally kidnapped and Cosmo decides the act was committed by one of the two gangs. He has her father (Herbert Rawlinson) place an ad in the newspaper that contact has been made with the kidnappers. Each gang thinks the other is pulling a double cross, and one gang wipes out the other.