FBI agent Wesley Doyle is startled by the spontaneous declaration of youngster Fenton Meiks about how his father's delusions to have a divine mission as avenging angel required him and his brother Adam to become his 'demon-slaying' murder accomplices. And how hard an dangerously revolting proved. But when Doyle accepts to be shown concealed victim graves, the plot twists in the present just as gruesomely.

In the midst of World War II, the battle below the seas rages. The Nazi's have the upper edge as the Allies are unable to crack their war codes. That is, until a wrecked U-boat sends out an SOS signal, and the Allies realise this is their chance to seize the 'enigma coding machine'. But masquerading as Nazi's and taking over the U-boat is the smallest of their problems. The action really begins when they get stranded on the U-boat.