Michael Evans and his paleontologist father have been invited by the mysterious time-traveling Shannon to visit the complex built around an underwater portal to the Jurassic period, but Mike uncovers a plot to steal one of the dinosaurs--and then Shannon and her trouble-making brother Jeff disappear through the portal.

Mike Evans goes through the time portal to find his friend Shannon and her troublesome brother Jeff, but he soon finds they all have bigger problems--a robot who wants to repopulate the Earth with dinosaurs and a group of Tyrannosaurus rex babies who remember Mike from New York.