The crew of the Odyssey, a space shuttle orbiting above the Earth's surface, looks on in horror as the Earth explodes before their eyes. Commander Chuck Taggart (Peter Weller), a geneticist (Sebastian Roche), Taggart's son (Christopher Gorham), a TV newswoman (Leslie Silva) and an astronaut (Tamara Craig Thomas) escape on a shuttle into space, where they're met by a mysterious being who offers to transport them back five years in time to try to save Earth. Armed only with a bit of computer code referring to "Leviathan," Taggart is determined to save the planet. But when the Odyessy crew discovers that even the smallest action on their part can quickly change the course of history in unexpected and potentially devastating ways, they must band together and proceed with caution for their rescue mission to succeed.