On a routine intern orientation day at the Eden Wildlife Zoo in northern Arizona, a glossy tour of the grounds masks a chaotic outbreak brewing in the clinic. A batch of monkeys is brought in after contracting a mysterious disease, and the veterinarians attempt a salvage operation with intracardiac epinephrine to restart a fallen animal. The procedure triggers a terrifying turn: the infection spreads through the room, transforming the primates into predatory zombies that launch violent attacks on the staff. One veterinarian is killed, and Dr. Gordon fights to stay alive as the alarms begin to echo through the facility.
As the campus residents arrive, the chaos cascades through the security perimeter. Johnny, a security team member, vows to check on the clinic but never returns. He is soon followed by the rest of the security crew, accompanied by college student Gage, who push toward the clinic only to discover Johnny and another veterinarian dead and Gordon barely clinging to life. The infected monkeys swarm the corridor, accelerating the carnage and claiming two guards. Only Gage, Rex, and newly hired Lizzy Hogan manage to slip away, starting a desperate retreat from the increasingly uncontainable outbreak.
Meanwhile, the zoo’s manager, Ellen Rogers, orders a full lockdown as fear and danger spread like wildfire across the grounds. The disease migrates into other animals with brutal efficiency: a group of wild hogs rampages through the park and attacks three students, forcing Lizzy, Gage, and Rex into a perilous sprint. The danger intensifies when infected giraffes lunge into the fray, killing two more students before the survivors manage to pull Amber, the last student, to safety. Gage sustains injuries, and while Lizzy and Rex tend to his wounds, Amber exploits the moment to steal their jeep, compelling the group to rely on a cluster of non-infected elephants for transport. Yet the elephants are spooked by a swarm of infected lemurs up in the treetops, tossing the trio from their backs and leaving Rex with a crushed leg.
Daxton, a zoo worker, and his intern A.J. defend themselves against the lemur threat and take shelter inside the gorilla lab. Daxton goes to check on the zoo’s endangered gorilla, Kifo, only to discover him infected. The confrontation turns deadly as Kifo kills Daxton and breaches the lab. Rex tries to stop the threat with a stab, but Kifo retaliates by crushing Rex’s head.
A separate rescue attempt unfolds when police arrive to neutralize the menace, only to be cut down by a pride of infected lions. Amber reaches the gate begging the lockdown to ease its grip, but she is mauled by a raging lion. The drama escalates when Ellen’s daughter, Thea, fights back against an infected koala with a baseball bat, killing it in a hard-won moment of courage. The koala’s blood prompts Ellen to investigate the pathogen further, discovering that an unknown enzyme found in the koala’s cerebral cortex is part of what spreads the disease. She urges the birdkeepers to release the birds to stem the infection, but the attempt proves futile.
Lizzy, Gage, and A.J. escape to the outer grounds, stumbling upon a dying Amber who drives their jeep. They fend off infected lions but are forced to crash the vehicle. In a bid to reach higher ground, they attempt a risky zipline ascent toward a watch tower, but A.J. slips away and dies. The remaining trio—Lizzy, Gage, and Ellen—reunite with Thea and formulate a plan that centers on the aviary: set the area ablaze to halt the airborne threat, and rescue Chelsea, a birdkeeper, along with her intern Ricky. They locate Ricky abandoned by the infected birds and Chelsea, who is alive yet grievously wounded, an infected bald eagle using her as a nest. The group realizes Ellen has already ignited the aviary, and they flee the fiery ruins just as another explosion from Ellen’s truck seals the birds’ fate.
The confrontation with Kifo resurfaces as the gorilla threat reemerges and the creature stalks the group to the gate. Ellen makes a dramatic stand, seemingly shooting Kifo to end his rampage. The survivors—Lizzy, Gage, Ellen, and Thea—are rescued by a helicopter, but a final, chilling postscript reveals that Kifo’s eyes open once more, signaling that the danger may not be over.
In the end, the film leaves a lingering note of peril, weaving a survival story across a zoo that becomes a trapped battleground where humans and wildlife contend with an inexplicable and spreading disease. The relentless sequence of animal attacks, the rapid collapse of security, and the quick escalation from containment to catastrophe frames a tense, multi-layered horror scenario that insists on looking at humanity’s hubris and vulnerability when faced with a pathogen that mutates the world’s most unexpected creatures.
