In 2267, Earth has just begun to recover from worldwide ecological disasters. Minh is part of the generation that first moved back up to the surface of the Earth from the underground hells. She's spent her entire life restoring river ecosystems, but lately her work has been stalled due to the invention of time travel. When she gets the opportunity take a team to 2000 BC to survey the Tigris and Euphratesrivers, she jumps at the chance to uncover the secrets of the shadowy think tank that controls time travel technology.