Chicago deputy district attorney Tony Warren is sent undercover by his boss, Martin Boland, to ascertain who has been swindling the members of the local Lonely Hearts clubs. Under the alias of oilman Tony Armstrong, Tony joins Lonely Hearts, Inc., where he immediately attracts the attention of lonely employees the Andrews Sisters, who work as both radio singers and secretaries for the club. Tony, however, is immediately attracted to another new member, Linda Mae Perkins. At the club's social, Patti Andrews dissuades the romantic interests of restaurateur Nick in order to chase after Tony. Tony's attentions, however, are directed to Colonel Thadious Winchester, a promoter who claims to own a new imitation rubber formula. The social is interrupted by a group of teenagers who have also rented the hall for a dance, and after some angry discussions, the two groups decide to combine their events. Later, Tony is enjoying a lunch date in the country with Linda when he is arrested for driving through a stop sign. When the county clerk insists on holding them until the judge returns from his vacation, Tony and Linda pretend to be eloping. As the clerk goes to get a justice of the peace, Tony overhears Linda on the phone and comes to suspect her as being one of the swindlers. Tony and Linda escape the county clerk and matrimony, and, a few days later, Nick agrees to sponsor the Andrews Sisters' radio program, during which Colonel Winchester announces his engagement to Miss Cavanaugh. Winchester further states that he is selling stock in his new imitation rubber corporation. After the broadcast, Linda convinces Winchester to hold his engagement party at Chez Nicholas. Before the party, however, Tony tells Linda who he really is, but she does not believe him. The engagement party is "crashed" by the teenagers, much to the chagrin of both Nick and Winchester. After selling Tony a thousand shares in his company, Winchester, who is actually a forger known as Indiana, and Miss Cavanaugh, who is bank robber Boston Kate, are arrested by detectives working with Linda, who is really Linda Harmon, an undercover agent for the Chicago police department. With the case solved and their true identities established, Tony and Linda are reunited.
