The solemn tones of Chopin's funeral march form a deadly background for Hop and Tank's latest and weirdest adventure. Bill King explained to them that a dozen guys have disappeared from a dozen parts of the country and nobody has ever heard about them again. They didn't have anything in common, except that when they vanished, somebody always whistled the funeral march. Enlisting the boys aid in his search for the mysterious whistling stranger - and they didn't have to go far before they felt his presence...