Unwillingly, and almost by accident, Boysie Oakes finds himself tackling `Operation Understrike'. When a routine mission to the United States suddenly goes wild, he is faced with the weighty responsibility of being British Special Security's observer at an important test-firing of Trepholite - a holocaustic missile designed to be launched from the latest thing in sub-aqua craft, USS Playboy. As the action moves at speed from New York to San Diego, Boysie meets a colorful cast of characters including his opponent Vladimir Solev, and the gorgeous Chicory Triplehouse.