The boys are riding in an educational orb when they decide to go off-road through a hedge - and bump into the giant Indominus Rex. After a bit of keepy-up with the orb, the glass is smashed and the boys escape - then do a Last of the Mohicans off a waterfall to safety. They reach the old visitor center, and hitch a ride back to base.
Meanwhile, Owen and Claire are tracking the boys, and find a path of destruction from Indominus who is killing other dinosaurs for fun.
Masrani, the wealthy Park Owner, mans-up, and leads the onsite security team in a chopper to drop a pay-load onto the animal, but only manages to crash the chopper into the giant Aviary, freeing hundreds of pteradactyls who fly to the main park entrance and start attacking the visitors. The nanny manages to find the boys - but is soon grabbed by a pterosaur who crashes into the central pool, and then both are promptly eaten by the huge sea beast.
Hoskins, the army guy from InGen, seizes control - and prepares to unleash the Raptors, with the unwilling help of Owen.
Together they hunt the Indominus Rex ... but soon the Raptors strike up a conversation with it, as they share the same DNA, and turn on the good guys.
Hoskins has had enough, and instructs his team to start dismantling the lab. The Raptors soon show up and take chunks out of him. They turn on Owen, but he manages to win them over again and they instead attack Indominus. All but one are killed, so the tech guy from New Girl opens the cage for the T-Rex, and the battle recommences.
T-Rex isn't faring so well, but Blue the Raptor tag-teams with him, and together they manage to knock Indominus into the big pool, where the sea beast snaps him up for supper. The animals retreat to the jungle, while the good guys are taken to an island base to be patched up, where Owen and Claire decide to give it another shot.