It's been eight years since Dr. Alan Grant (SAM NEILL) survived the mishaps and chaos that surrounded the now defunct Jurassic Park tourist attraction on Isla Nublar where scientifically cloned dinosaurs ran amok and killed many people. Still working as a low-paid paleontologist on various dinosaur dig sites in Montana with his assistant, Billy Brennan (ALESSANDRO NIVOLA), Grant has vowed that nothing could ever make him set foot on that island again.
Yet, when wealthy adventurers Paul (WILLIAM H. MACY) and Amanda Kirby (TÉA LEONI) offer to fund his work if he'll be their guide as they fly over Isla Sorna, an adjacent island also owned by the corporation, InGen, that ran the first, Grant reluctantly agrees.
Even so, he's shocked when the small plane carrying him, Billy, the Kirbys and their crew consisting of
Udesky (MICHAEL JETER), Cooper (JOHN DIEHL) and Nash (BRUCE A. YOUNG) lands on the island. It turns out that Paul and Amanda aren't adventurers after all, but instead are the divorced parents of 12-year-old Eric (TREVOR MORGAN) who's now been missing for eight weeks after an accident left him and Amanda's boyfriend stranded on the isle.
Knowing full well what they're up against, Grant immediately sets out for the coast, hoping to find a way off the dangerous land. As he and the others set out to do so and hopefully find Eric in the process, they must not only contend with the usual dinosaurs, such as T-Rexes and raptors, but also the flying Pteranodons and the massive Spinosaurus, a huge carnivore that's adept both on land and in the water.