Wayne's invention succeeds in finding gold - a pot of doubloons claimed by a leprechaun, who puts a curse on the Szalinskis until they hand it over.

To return from a time trip to 1864 Colorado, the Szalinskis must help an alien recover his starship from a ruthless gang, who master the alien's weapons and defenses.

Wayne's chemical to increase intelligence has different effects on the family, including mind reading and levitation, while their dog, Quark, is able to hypnotize people.