Warrwen Hamilton and Martin Crane, chief executives if the World-Wide Insurance Company, enlist the aid of the Masked Marvel to find Mura Sakima, a former Japanese envoy, whom they suspect of being responsible for extensive sabotage of war industries. But CRane is secretly in league with Sakima, and they arrange for Hamilton's murder. The murdered man's daughter, Alice, joins the Masked Marvel and his three aides in a campaign to expose and apprehend Sakima. The Masked Marvel is one of four men - Bob Barton, Frank Jeffers, Terry Morton and Jim Arnold; he hides his identity beneath a black mask and only Alice knows he is one of the four investigators.