Muldoon and Gennaro go out to investigate the hadrosaur stampede. Arnold informs them that he has found Nedry. Once they reach him, they retrieve the rocket launcher and leave Nedry's carcass to the compys, which Gennaro notices have five-fingered hands. Grant and the kids float under the giant dome of the park's aviary.
Arnold monitors the motion sensors but is unable to locate either the t-rex or Grant and the kids. Malcolm claims that a part of his theory, the "Malcolm Effect," indicates that a catastrophic event will happen when it appears the system is working perfectly.
Inside the aviary, Grant and the kids are looking for motion detectors and are attacked by fiercely territorial cearadactyls, large fish-eating pterodactyls. One of them tries to pick up Lex, but Grant fights it off. They escape back to the raft. Unsure what to do when they are confronted by a group of poisonous dilophosaurs by the shore, Grant and company are saved when the t-rex reappears and distracts the dilophosaurs long enough to allow the raft to pass.
Arnold finally locates the t-rex, and Muldoon and Gennaro go to catch it. Muldoon fires two rocket-launched doses of tranquilizer at the tyrannosaur but seems to miss, and they are forced to flee. The t-rex turns around and again chases Grant and the kids, who fall down a waterfall. Lex narrowly escapes the tyrannosaur, nearly drowning in the process. They run behind the waterfall to escape, and Grant finds a maintenance door and enters it, only to be trapped inside. He finds a flashlight, a baby male velociraptor, and an electric go- cart. Outside, the t-rex finds the kids behind the waterfall and starts dragging Tim out with its tongue. Suddenly, the dinosaur keels over.
Arnold reports that the t-rex finally succumbed to its tranquilizer dose, as Muldoon had not missed after all. Just as Arnold is gloating that things are back in order, he notices that the park has been running on its auxiliary power, and that the power has suddenly run out. He realizes there was a mix-up when he shut the power off earlier. Meanwhile, the waterfall stops flowing and the maintenance door opens, releasing Grant.
Back at the control room, Wu reads a printout that indicates that the electric fences have been off for the last five hours. Arnold goes out to try to turn the generator back on, but is killed by a velociraptor. Muldoon and Gennaro narrowly escape the pack of raptors, but Gennaro is attacked by a raptor when he goes back to the generator to try to turn it on again.