A young boy and a girl with a magic crystal must race against pirates and foreign agents in a search for a legendary floating castle.

Young orphan Sheeta and her kidnapper, Col. Muska, are flying to a military prison when their plane is attacked by a gang of air pirates led by the matronly Dola.

Escaping from a mid-air collision via a magic crystal around her neck, Sheeta meets fellow orphan Pazu and the pair join forces to discover the mystical floating city of Laputa while pursued by both Muska and the pirates, who lust for the city's myriad treasures.