A German U-boat embarks on a horrifying journey after one of its crew claims a strange souvenir in this tale by the author of "The Call of Cthulhu". During World War I, a German U-boat sinks a British freighter. Karl Heinrich, Graf von Altberg-Ehrenstein, a lieutenant-commander in the Imperial German Navy, orders the ship to fire on the British survivors and their lifeboats before submerging. After the U-boat surfaces again, a dead sailor is found clinging to the deck with a mysterious ivory talisman in his pocket. Heinrich's second-in-command pockets the charm just before the body is thrown overboard. And thus begins the ship's journey into madness . . .