Identical twins Sean and Eric Gabrielson — one a paleontologist, the other a physicist — have been selected as mankind's first time travelers. Together they set out from Time Zero, 2016, in opposite directions — one toward the past to see dinosaurs walk the earth; the other towards the future to learn the secrets of the gods. Somewhere beyond the eons and the ages they will reach Time Ultimate — and the secret that has eluded mankind since time began.