Down-on-their luck brothers, Lars and Ernie Smuntz, aren't happy with the crumbling old mansion they inherit... until they discover the estate is worth millions. Before they can cash in, they have to rid the house of its single, stubborn occupant—a tiny and tenacious mouse.
Stan and Ollie are mousetrap salesmen hoping for better business in Switzerland, with Stan's theory that because there is more cheese in Switzerland, there should be more mice.
A woman is murdered and a hand bill of a resort run by a young couple is found. Is the murderer headed for it? Who is next victim? All the boarders, including owners are under false name. Why? A policeman arrives, will he be able to stop?
Tom designs a better mousetrap that would have made Rube Goldberg jealous. While he sleeps, the mouse that Tom drew wakes Jerry and they get chased by the cat Tom drew. As Tom awakes, they make a strategic alteration to the design.