Four years after Jurassic Park was overrun by cloned dinosaurs on the Central American island of Isla Nublar, a young girl named Cathy Bowman wanders around on nearby Isla Sorna during a family vacation, and survives an attack by a swarm of Compsognathus. Her parents file a lawsuit against the genetics company InGen, now headed by John Hammond's nephew, Peter Ludlow, who plans to use Isla Sorna to relieve the company of financial losses. Mathematician Dr. Ian Malcolm meets Hammond at his mansion. Hammond explains that Isla Sorna, abandoned years earlier during a hurricane, is where InGen created their dinosaurs before moving them to Jurassic Park on Isla Nublar. Hammond hopes to stop InGen by sending a team to Isla Sorna to document the dinosaurs, to help rally public support against human interference on the island. After learning that his girlfriend, paleontologist Dr. Sarah Harding, is part of the team and is already on the island, Ian agrees to go to Isla Sorna, but only to retrieve her.
Ian meets his teammates, Eddie Carr, an equipment specialist and engineer, and Nick Van Owen, a video documentarian. After arriving on the island, they locate Sarah and discover that Ian's daughter, Kelly, had stowed away in a trailer being used as a mobile base. They then watch as an InGen team of mercenaries, hunters and paleontologists led by Ludlow arrive to capture several dinosaurs. Meanwhile, team leader Roland Tembo hopes to capture a male Tyrannosaurus by luring it to the cries of its injured infant. That night, Ian's team sneak into the InGen camp and learn the captured dinosaurs will be brought to a newly proposed theme park in San Diego. This prompts Nick and Sarah to free the caged dinosaurs, wreaking havoc upon the camp.
Nick also frees the infant T. rex and takes it to the trailer to mend its broken leg. After securing Kelly with Eddie, Ian realizes the infant's parents are searching for it and rushes to the trailer. As soon as Ian arrives, the infant's parents emerge on both sides of the trailer. The infant is released to the adult T. rexes, which then attack the trailer, pushing it over the edge of a nearby cliff. Eddie soon arrives, but as he tries to pull the trailer back over the edge with an SUV, the adult T. rexes return and devour him. The trailer and the SUV both plummet off the cliff. Ian, Sarah, and Nick are rescued by the InGen team, along with Kelly. With both groups' communications equipment and vehicles destroyed, they team up to reach the old InGen compound's radio station on foot.
The next night, the two adult T. rexes find the group's camp. The female T. rex chases the group to a waterfall cave, while Roland tranquilizes the male. Much of the remaining InGen team is killed by Velociraptors while fleeing through a tall grass savannah. Nick runs ahead to the communications center at the InGen Worker's Village to call for rescue. When Ian, Sarah and Kelly arrive, they are attacked by the raptors. They evade the raptors until a helicopter arrives and transports them off the island.
A freighter transports the male T. rex to the mainland, but crashes into the dock after the crew is killed by a creature of unknown species. A guard opens the cargo hold, accidentally releasing the T. rex, which escapes into San Diego and goes on a rampage. Ian and Sarah retrieve the infant T. rex from a secure InGen building and use it to lure the adult back to the ship. Ludlow tries to intervene but is trapped in the cargo hold by the adult T. rex and mauled by the infant. Before the adult can escape again, Sarah tranquilizes it while Ian closes the hold. The T. rexes are escorted back to Isla Sorna, and Hammond says that the American and Costa Rican governments have agreed to declare the island a nature preserve, affirming that "life will find a way".
Output: Why does Doctor Ian Malcolm agree to go to Isla Sorna?