From their rented room in the gloomy old castle of eccentric Professor Danforth and his lovely daughter Carol (Carol Christensen), the Three Stooges learn of a Martian spy who's posing as a servant in order to get at the Professor's new invention -- a combination submarine-helicopter-tank. But when Air Force Captain Tom Andrews (Edson Stroll) arrives to test the machine, he finds he's more interested in Carol as the Stooges soon turn the whole demonstration into a complete shambles. After capturing the machine, the Martian spies go winging through space with the Stooges clinging to its side. And once the three heroes manage to destroy the all-purpose military weapon and its alien passengers, they finally make their own hilarious escape.