Plot summary
The narrative begins in August 1989 by slowly tying together a series of incidents involving strange animal attacks in Costa Rica and on Isla Nublar, the main setting for the story. One of the species, a strange small lizard-like creature with three toes, is identified later as a Procompsognathus. Paleontologist Alan Grant and his paleobotanist graduate student, Ellie Sattler, are abruptly whisked away by billionaire John Hammond—founder and chief executive officer of International Genetic Technologies, or InGen—for a weekend visit to a "biological preserve" he has established on a remote island off the coast of Costa Rica.
Upon arrival, the preserve is revealed to be Jurassic Park, a theme park showcasing cloned dinosaurs. The animals have been recreated using damaged dinosaur DNA found in mosquitoes preserved in prehistoric amber. Gaps in the genetic code have been filled in with reptilian, avian, or amphibian DNA. To control the population, all specimens on the island are lysine-deficient females. Hammond proudly touts InGen's advances in genetic engineering and shows his guests through the island's vast array of automated systems.
Recent events in the park have spooked Hammond's investors. To placate them, Hammond means for Grant and Sattler to act as fresh consultants. They stand in counterbalance to a well-known mathematician and chaos theorist Ian Malcolm and a lawyer representing the investors, Donald Gennaro. Both are pessimistic about the park's prospects. Malcolm, having been consulted before the park's creation, is especially emphatic in his prediction that the park will collapse, as it is an unsustainable simple structure bluntly forced upon a complex system.
Countering Malcolm's dire predictions with youthful energy, Hammond groups the consultants with his grandchildren, Tim and Alexis "Lex" Murphy. While touring the park with the children, Grant finds a Velociraptor eggshell, which seems to prove Malcolm's earlier assertion that the dinosaurs have been breeding against the geneticists' design. Malcolm suggests a flaw in their method of analyzing dinosaur populations, in that motion detectors were set to search only for the expected number of creatures in the park and not for any higher number. The park's controllers are reluctant to admit that the park has long been operating beyond their constraints. Malcolm also points out the height distribution of the Procompsognathus forms a Gaussian distribution, the curve of a breeding population, rather than the distinctive pattern that a population reared in batches ought to display.
In the midst of this, the chief programmer of Jurassic Park's controlling software, Dennis Nedry, attempts corporate espionage for Lewis Dodgson, a geneticist and agent of InGen's archrival, Biosyn. By activating a backdoor he wrote into the park's computer system, Nedry manages to shut down its security systems and quickly steal frozen embryos, two for each of the park's fifteen species. He then attempts to smuggle them out to a contact waiting at the auxiliary dock deep in the park; however, during a sudden tropical storm, he exits his stolen vehicle to get his bearings and is killed by a Dilophosaurus. Without Nedry to reactivate the park's security, the electrified fences remain off, and dinosaurs escape. The adult and juvenile Tyrannosaurus Rex attack the guests on tour, destroying the vehicles, killing public relations manager Ed Regis, and leaving Grant and the children lost in the park.
Malcolm is gravely injured during the incident but is soon found by Gennaro and park game warden Robert Muldoon and spends the remainder of the novel slowly dying as, in between lucid lectures and morphine-induced rants, he tries to help those in the main compound understand their predicament and survive.
The park's upper management—engineer and park supervisor John Arnold, chief geneticist Henry Wu, Muldoon, and Hammond—struggle to return power to the park, while the veterinarian, Dr. Harding, takes care of the injured Malcolm. For a time they manage to get the park largely back in order, restoring the computer system by shutting down and restarting the power, resetting the system. Unfortunately, a series of errors on their part soon plunge the park into greater disarray. During their time trying to restore the park to working order, they fail to notice that the system has been running on auxiliary power since the restart; this power soon runs out, shutting the park down a second time. Furthermore, since the auxiliary generators didn't create enough electricity to power the fences, they weren't reactivated when the system was reset, meaning all the fences—including the holding pen containing the park's Velociraptors, quarantined due to their intelligence and aggression—had been offline the whole time. Escaping their enclosure, the raptors kill Wu and Arnold and injure Muldoon, Gennaro, and Harding. Meanwhile, Grant and the children slowly make their way back to the Visitor's Center by rafting down the jungle river, carrying news that several young raptors, bred and raised in the island's wilds, were on board the Anne B, the island's supply ship, when it departed for the mainland.
While Ellie distracts the raptors, Grant manages to turn the park's main power back on. After escaping from several raptors, Grant, Gennaro, Tim, and Lex are able to make it to the control room, where Tim is able to contact the Anne B and tell them to return. The survivors are then able to organize themselves and eventually secure their own lives. Word soon reaches them that the crew of the Anne B has discovered and killed the raptor stowaways.
Gennaro tries to order the island destroyed as a dangerous asset, but Grant rejects his authority, claiming that even though they cannot control the island, they have a responsibility to understand just what happened and how many dinosaurs have already escaped to the mainland. Grant, Ellie, and Muldoon set out into the park to find the wild raptor nests and compare hatched eggs with the island's revised population tally. Cautious in this pursuit, they emerge unharmed. Meanwhile, Hammond, taking a walk around the park and contemplating making a park improving on his previous mistakes, hears the T-Rex roar and falls down a hill where he is eaten by a pack of Procompsognathus. Concerning the dinosaurs' breeding, it is eventually revealed that using frog DNA to fill gaps in the dinosaurs' genetic code enabled a measure of dichogamy, in which some of the female animals changed into males in response to the all-female environment.
In the conclusion, before boarding helicopters, the group tell the Costa Rican Air Force that the dinosaurs had been killing people. The Air Force then say that the island is dangerous and releases napalm over the island, destroying the island and the dinosaurs. It is implied that Malcolm dies. Survivors of the incident are indefinitely detained by the United States and Costa Rican governments. Weeks later, Grant is visited by Dr. Martin Guitierrez, an American doctor who lives in Costa Rica and has found a Procompsognathus corpse. Guitierrez informs Grant that an unknown pack of animals has been migrating through the Costa Rican jungle, eating lysine-rich crops and chickens. He also informs Grant that none of them, with the possible exception of Tim and Lex, are going to leave any time soon.
