The film depicts the misadventures of Lou Francis and Bud Alexander, two private detectives investigating the murder of a boxing promoter.

The film was part of a series in which the duo meet classic characters from Universal's stable, including Frankenstein, the Mummy and the Keystone Kops.

Tommy recently escaped from jail after being accused of murdering his manager, and asks the duo to accompany him on a visit to his fiancée, Helen Gray.

Detective Roberts questions Dr. Gray and Helen while Bud and Lou search for Tommy.

Tommy, still invisible, gets into the ring with them and again knocks out Hanlon, making it look like Lou did it, and an official match is arranged.

The characters' surnames "Alexander" and "Francis" are Abbott's and Costello's real middle names.

When asked by a reporter whom he has fought in the past, Lou answers, "Chuck Lamont, Bud Grant".