In earlier books, Jim has taken his readers from an early 1942 incident in which a British Destroyer was shadowing a German U-boat through the TOTO channel. The U-boat had made a dive into the depths of the channel, the Destroyer's sonar then picked up a second object that apparently traded shots with the U-boat. The U-boat was destroyed, then the Destroyer's sonar picked up the second object's exit of the area at what the Captain had lodged as...