The Investigator, an omniscient being from another galaxy, has come to Earth to rid it of evil and corruption. To assist him, he has recruited two young Americans, John and Julie , whom he has miniaturised and given special powers. In a cave on Malta, the Investigator gives John and Julie their first assignment: they are to foil crooked entrepreneur Stavros Karanti's plan to steal a priceless Raphael painting from St John's Cathedral in Mdina.