Mild mannered Dr. Howard Bannister is a professor of musicology at the Ames Conservatory of Music in Ames, Iowa. With his straight laced and controlling fiancée Eunice Burns, Howard is in San Francisco to attend the Congress of American Musicologists convention hosted by Frederick Larrabee. The Larrabee Foundation has shortlisted two finalists for the $20,000 Larrabee Grant, the two being pompous Hugh Simon and Howard, whose research involves prehistoric man making music with igneous rocks. Howard's life in San Francisco is turned upside down when he meets Judy Maxwell, a klutzy, directionless but brilliant young woman whose life is spent studying at one educational institution after another, her stint at each being until she's kicked out. It's love at first sight for Judy, who does whatever she can to insinuate herself into Howard's life. Further complications ensue as Howard, Judy, wealthy Mrs. Van Hoskins and reporter Mr. Smith - the latter two who are staying at the same hotel as Howard - all have the identical red plaid overnight bag respectively carrying Howard's igneous rocks, Judy's clothes, Mrs. Van Hoskins jewels and top secret government documents, the latter two which are eyed by others who are trying to get their hands on the contents.