Jurassic Park is an action thriller directed by Steven Spielberg about dinosaurs genetically reproduced by a scientist for a theme park which get out of control and run amok, resulting in the need to stop them.
On the volcanic island of Isla Nublar, an InGen employee is attacked and killed by a Velociraptor, possibly a pack leader known as The Big One, while attempting to transport it to a heavily fortified enclosure. This prompts the worker's family to file a lawsuit against the company, and it successfully scares InGen's investors into thinking that the park is not safe. The CEO of InGen, John Hammond, decides to reassure the investors by bringing a group of experts to his park in order to gain their approval of it. Among the group he invites Paleontologist Dr. Alan Grant and Paleobotanist Dr. Ellie Sattler, two scientists whose digs he's been funding, Ian Malcolm a mathematician (or "Chaotician" as he calls himself) and his investor's lawyer, Donald Gennaro. Meanwhile in Costa Rica, Dennis Nedry is meeting with Lewis Dodgson, a rival scientist of InGen working for Biosyn. Dennis is a computer programmer working for John on Isla Nublar and has recently become dissatisfied with his treatment by InGen. Dennis agrees to steal dinosaur embryos for Dodgon for a price.
The group assembled by John arrive on the island via helicopter and then take two jeeps out into the park, where they come across a Brachiosaurus and a herd of Parasaurolophus, to their utter amazement. John then takes his stunned guests to the Visitor Center, where they see a birth to an infant Velociraptor and learn that InGen were able to recreate dinosaurs using DNA taken from mosquitoes who had feasted on dinosaur blood, and had been preserved in amber. The DNA taken from the mosquitoes was spliced with DNA from frogs to fill in the gaps of the genetic code. InGen scientists only cloned female dinosaurs, thus eliminating the threat of uncontrolled breeding of the animals.
They are then taken to the Velociraptor enclosure at Alan's request where they meet park warden Robert Muldoon. Robert tells the group about how vicious and intelligent the raptors are. He explains there are only three raptors all together because The Big One, who has taken over as the alpha female, had "killed all but two of the others", a total of eight raptors. Meanwhile, the scientists lower a cow into a dinosaur's enclosure and observe it eating the cow, destroying the support cables and fabric harness in the process. After the experiment, the scientists head indoors for lunch.
During the lunch Alan, Ian and Ellie start to express doubt in the park after the initial shock has worn off. Ian questions the ethical morality in cloning species that had not lived for thousands of years. Ellie expresses concern that the scientists may not be thinking of the repercussions that might occur of what they are cloning. Alan remains fairly neutral on the issue though he advises John to be careful. Donald is the only one who completely approves, thanks to the amounts of money they could make off the island. Hammond puts it eloquently "I don't believe it. You're meant to come down here and defend me against these two characters and the only one I have on my side is the blood-sucking lawyer!"
After the lunch, the team will start on a tour through the park. The visitors are toured around in electric Tour Vehicles. John's grandchildren, Lex and Tim Murphy, also take the tour. Both of them instantly take a liking to Alan, who doesn't appreciate the attention as he dislikes children. While on the tour, a goat is released out in the wild close to the fence to attract the dinosaur and eat it, while the visitors observe it. The tour goes disappointingly, with most of the dinosaurs failing to appear. Ellie leaves the tour to take care of a sick Triceratops with the veterinarian Dr. Harding.
A tropical monsoon storm hits the island, and most InGen employees leave, except for John, game warden Robert, and chief systems engineer Ray Arnold. During the storm, Dennis shuts down park security (except for the raptor fences) and as a result, the Tyrannosaurus breaks through the deactivated electric fence surrounding its pen, kills and eats the abandoned goat and devours Donald, attacking Tim and Lex hiding in the car, which gets submerged partway into a swamp of mud and wounding Ian. The children and Alan only narrowly avoid being killed.
Just after they flee the wreckage, Ellie and Robert arrive. At first, they believe the only survivor of the attack is Ian, but upon further investigation they find two footprints: one is Alan's and one belongs to one of the kids. Just then, the Tyrannosaurus returns, and Ian, Robert, and Ellie barely escape her in their jeep. Meanwhile, Dennis crashes his car, and while trying to winch it, he is killed by a juvenile Dilophosaurus, who spits out a tar-like venom at him before devouring the obese saboteur in his Jeep.
Alan, Tim, and Lex spend the night in a tree. While hiking to safety the next morning, they discover hatched eggs, which means that the dinosaurs are actually breeding. Alan hypothesizes that the frog DNA is responsible: some species of frog are known to spontaneously change sex in a single-sex environment.
Ray tries to hack Dennis' computer to turn the power back on but fails, so he does a full system restart, which requires the circuit breakers to be manually reset from the utility shed. When he does not return, Ellie and Robert follow and discover the raptors have escaped; the shutdown cut off power to the electric fences around their pit. Robert realizes that they are near and tells Ellie to go to the utility shed herself and turn the power back on while he tries to hunt them down. The raptors set a trap for Robert and he is tackled and killed by The Big One. Ellie escapes from another after discovering Ray's severed arm in the maintenance shed. After managing to turn on the power and escaping the raptor, she meets Alan, and they both go back to Ian and John in the emergency bunkers. Lex and Tim narrowly escape The Big One and her fellow raptor in the kitchen ( locking one in the freezer and knocking The Big One out for several minutes), and Lex is finally able to restore the Park's computer systems in order to call John to request a helicopter rescue of the survivors.
Alan and Ellie hold off The Big One trying to open the door to the computer room, until the power is restored, and the electromagnetic locks begin working. With the door secures, the raptor breaks into the room through the window after Grant shoots at it through the glass, and the group climbs up into the ceiling crawlspace and arrive at the Visitors Center skeleton display, only after Lex is almost killed by The Big One leaping up at her. The raptors pursue and after a scuffle with The Big One on top of the fossil exhibits and the raptors block their escape route, help comes from an unlikely source when the Tyrannosaurus suddenly appears and kills both raptors, saving Alan, Ellie, Lex, and Tim in the process. The four then climb into John and Ian's jeep and leave. Alan says he will not endorse the park, a choice with which John concurs. As all fly away in the helicopter, the children fall asleep beside Alan, who contemplatively watches a flock of pelicans flying nearby, the surviving relatives of the dinosaurs they escaped.