The Eden Wildlife Zoo, a zoo in northern
Arizona containing rare animals, is having its intern orientation day, where college students applying for jobs as interns are touring the zoo. Meanwhile, some of the zoo's monkeys contract an unknown disease and are taken to the clinic, where the veterinarians use intracardiac
epinephrine to save the life of a monkey that suffered a
cardiac arrest. The contagious pathogen spreads to all of the
monkeys in the room, turning them into zombies with predatory behavior towards humans. They attack the veterinarians and kill one of them, while the remaining one, Dr. Gordon, manages to activate an alarm. As the college students arrive, the alarm reaches the zoo's security. One of the security team members, Johnny, decides to check on the veterinarians himself. When he doesn't return, the security team, accompanied by college student Gage, make their way to the clinic. Once there, they discover Johnny and one of the veterinarians dead, and Gordon barely alive. The monkeys violently attack the group, killing two guards. Gage, head of security Rex and newly hired Lizzy Hogan manage to escape. Ellen Rogers, the manager of the zoo, gets word of the mayhem and puts the zoo on lockdown. The disease spreads throughout the zoo, infecting a group of
wild hogs that attack three of the students. Lizzy, Gage and Rex arrive just as the students are then attacked by infected
giraffes, which kill two of them. They rescue the remaining student, Amber, but Gage is injured, and as Lizzy and Rex tend to Gage's wounds, Amber steals their jeep, forcing them to use a group of non-infected
elephants as transportation. But along the way, the elephants become spooked by a group of infected lemurs in the nearby trees, throwing Lizzy, Rex, and Gage from their backs. In the ensuing chaos, Rex's leg is crushed by one of the elephants. One of the workers, Daxton, and his intern A.J. fend off the lemurs, and the group takes refuge inside the gorilla lab. Daxton goes to check on the zoo's endangered
gorilla, Kifo, finding him infected. Kifo kills him and invades the lab. Rex stabs him, but Kifo crushes his head in retaliation. Meanwhile, a police team arrives at the zoo to attempt to eliminate the threat but are killed by a pride of infected
lions. Amber reaches the front gate and demands that Ellen, who is watching over the security cameras, open it, but is mauled by an infected lion. Ellen's daughter Thea is attacked by an infected
koala, but she kills it with a baseball bat. Ellen inspects the koala's blood and discovers that the disease was created by an unknown enzyme found in the koala's
cerebral cortex. She encourages birdkeeper Chelsea to release the birds to prevent them from being infected, to no avail. Lizzy, Gage and A.J. escape and find a dying Amber driving their jeep, and they are attacked by the infected lions. They kill the lions but accidentally crash the jeep. They then attempt to reach the watch tower by using an unfinished zipline, but A.J. falls to his death. Lizzy and Gage reunite with Ellen and Thea, and they theorize that the
birds have become infected. They decide to set the aviary on fire using gas cans, but before they do so, Lizzy and Gage go inside to rescue Chelsea and her intern Ricky. They soon find Ricky, killed by the infected birds, and Chelsea alive but eviscerated, with an infected
bald eagle using her as a nest. Lizzy and Gage notice smoke rising, realize that Ellen has begun burning the aviary down, and manage to escape. They set off an additional explosion using Ellen's truck, killing the birds before they can break out of the aviary. Kifo then appears and chases the group to the gate, where Ellen seemingly shoots him to death. The four are then rescued by a helicopter. However, after they are picked up, Kifo opens his eyes, revealing he is still alive. == Cast ==