The film centers on a group of Navy SEALs, led by American Dr. Frank Reno, who once worked on the Philadelphia Experiment. The film begins in 1998, when Reno has purportedly perfected time travel technology. The SEALs use it to travel backwards to the year 112,000,000 BC of the Early Cretaceous, in order to rescue a previous, 1949 expedition led by Reno's brother Erik. Reno's team arrives in Laurasia six years after the 1949 team arrived, to find only a few survivors. The SEAL team is ill-equipped for the dangers of this prehistoric period, and is decimated by a Tyrannosaurus rex and other prehistoric life. Having accomplished their mission, remnants of the two teams merge into one and return to the present, but in the process the anomaly malfunctions, allowing the subadult,, Tyrannosaurus to travel to the present and wreak havoc in rural Los Angeles. Reno stays behind, ostensibly to close the portal, but instead transports himself to the year 1950 after being cornered by the dinosaur. Apparently he tried to leap through the portal as it closed, but was sent to 1950 instead of 1998. In the present, survivors of the team run through the Suburbs of Los Angeles, barely evading the rampaging prehistoric beast. Meanwhile, in 1950, the wounded Dr. Reno arrives and meets up with the younger version of himself. The old Reno teaches the young Dr. Reno how to correctly use the time-travel technology before dying. Young Dr. Reno assembles a strike team of soldiers and leads them through the portal to 1998, where they attempt to rescue the remainder of the original team from the rampaging dinosaur. Young Reno then has to find a means of luring the creature back into the anomaly and returning it to its own time, before it takes the life of his brother from him once more. Finally the dinosaur is banished back to its time where the trip fuses it with a mountain, killing it. Frank opens a portal to 1950 for everyone to return home through. Frank and one of the rescued team members plan to start a relationship. Someone needs to stay behind to close the portal, Erik does, his lover Betty staying with him. The two plan to catch up with the group's old selves.
