The story begins in 1944 in the Pacific Ocean, where Lieutenant William Kenlon of the U.S. submarine Sea Serpent observes a strange, large, winged human flying overhead. The creature, one of the “winged men,” attaches a mysterious device to the submarine’s hull. When the crew captures the being and attempts to remove the device, the Sea Serpent is suddenly transported thousands of years into a future where chemical experiments have rendered the land uninhabitable. In this future, humanity has evolved into two warring factions: the winged people of the air and the amphibian people of the sea. The winged people, who have brought the submarine forward in time, want the crew to use their military technology to destroy the amphibians’ underwater city. Kenlon and the crew must navigate this strange new world, encountering other time-displaced vessels and facing complex moral decisions about which side to support. Kenlon, in particular, undergoes hallucinatory experiences where his consciousness is transferred into the bodies of both a winged person and an amphibian, giving him perspective on both sides of the conflict. Ultimately, Kenlon chooses to disable the infrastructure of both warring factions, forcing peace, before he and the Sea Serpent are returned to their own time.
