As the world comes to terms with the horror of nuclear terrorism another even more devastating threat emerges. But who is behind this and what are their intentions? With only scraps of evidence to go on two British officers, Jack Riley and Helen Bascombe, uncover a plot involving a secret religious sect whose family histories can be traced back to the Crusades. The search for the conspirators takes place against a backdrop of deteriorating relations with the USA where the President prefers the affairs of the bedroom to the affairs of State. When British and American nuclear missile submarines start playing cat and mouse in the North Atlantic they eventually run out of room to manoeuvre and there follows a desperate race against time to prevent a global disaster that would threaten the future of mankind.