Maurice Courtelin, a Parisian tailor (Maurice Chevalier), is owed a great sum of money by a viscount (Charles Ruggles). Stalling for time, the titled but penniless nobleman moves Maurice into the family chateau and passes him off as a baron. The beguiling Maurice soon charms the entire aristocratic household, except for the haughty Princess Jeanette (Jeanette MacDonald), who remains suspicious of him. But suspicion eventually gives way to love.
Gangster Frank Olins is to die in the gas chamber much to the dismay of his girlfriend Margot Shelby as he is carrying the secret of the location of $400,000 with him. Margot seduces gangster Jim Vincent to get him to engineer the removal of Olins' body from the prison immediately after he dies in the gas chamber. She takes prison doctor Craig away from his nurse/girl friend and gets him to administer an antidote for cyanide gas poisoning. During the removal of Olins' body, the hearse driver is killed by Tommy. The revived Olins gives Margot half of a map showing the money location and Vincent, in a fit of jealousy, kills Olins and takes the ...
In 19th Century Paris, the maniacal Dr. Mirakle abducts young women and injects them with ape blood in an attempt to prove ape-human kinship. He constantly meets failure as the abducted women die. Medical student Pierre Dupin discovers what Mirakle is doing too late to prevent the abduction of his girlfriend Camille. Now he desperately tries to enlist the help of the police to get her back.
Waldo and Irene have been living with Margit for the four years that they have been engaged. Margit has planned the wedding and the honeymoon - in fact, Margit plans everything down to what they will have for breakfast every day. The only problem is that Waldo is a milquetoast and Irene does not want to be married to a milquetoast. So she says she is in love with Charlie, a bohemian artist/producer who lives in a trailer behind Spike's Place. When Margit confronts Charlie about giving up Irene, Charlie sees that she is the one for him. To make everyone happy, Charlie will have to help Waldo get a backbone.
Lou Costello plays a country bumpkin vacuum-cleaner salesman, working for the company run by the crooked Bud Abbott. To try to keep him under his thumb, Abbott convinces Costello that he's a crackerjack salesman. This comedy is somewhat like "The Time of Their Lives," in that Abbott and Costello don't have much screen time together and there are very few vaudeville bits woven into the plot.