In the expansive and vibrant Colepepper Zoo, a young timber wolf named Gracie lives alongside her protective pack and her particularly anxious grandmother, Gramma Abigail. Gramma Abigail takes it upon herself to train the pack for what she believes are inevitable disasters, instilling in them a deep distrust of all the other animals in the zoo, especially with the arrival of a new creature in a nearby enclosure as the zoo prepares to close its doors for the day.
Simultaneously, a catastrophic event occurs in space—a meteorite collides with a satellite, sending debris hurtling towards Earth. One chunk of the meteorite crashes through the zoo's wolf den and lands in the "Kuddle Korner" petting zoo. There, a curious bunny unknowingly consumes the alien-infused material, becoming a host for a potent virus and subsequently incubating it within a disturbing purple pod. The fallout from this meteor strike enables Gracie to escape her confined enclosure to investigate the peculiar pod, but her curiosity is met with danger when a gummi-like arm suddenly emerges, reaching out to snatch her. Fortunately, she manages to elude the grasp just in time to meet Dan, a wild mountain lion who is also the new arrival. However, their encounter is cut short when a zookeeper, oblivious to the chaos unfolding, tranquilizes them both and places them in the vet station, leaving the zoo unattended.
In the barn, the pod opens, unveiling the bunny transformed into a grotesque creature dubbed "Bunny Zero"—a horrifying, indestructible gummi-like zombie that now threatens all the animals in the zoo. As it breaks free and begins to infect creatures left and right, including an infected gorilla named Fred that another animal, Felix, once abandoned, Gracie and Dan team up alongside a handful of other unaffected animals: Xavier, a red ruffed lemur known for his self-inflicted injuries and faked ailments; Frida, a bold capybara; and Ash, a sarcastic ostrich.
The dynamic shifts dramatically as they navigate the dangerous zoo environment, eventually deciding to split up after a tense encounter with Fred. Felix, Frida, Ash, and Xavier attempt to find safety in the gift shop, while Gracie makes a pact with Dan. She promises to give him the zoo key for a chance to escape to the wild if he helps her locate her pack. As they battle their way past numerous Gum-beasts, including the menacing Bunny Zero, Gracie and Dan stumble upon the zoo's only remaining uninfected animal, a young pygmy hippo named Poot, who is humorously hiding in a ball pit. Gracie cleverly convinces Poot to join their group by assuring her that she and Dan won’t eat her… unless they find themselves starving.
However, when they finally reach the wolf enclosure, Gracie is heartbroken to discover that her entire pack has been transformed into Gum-beasts. This brings about a heated argument between her and Dan, just as the attractions powered back on from the gift shop, escalating the danger as they are besieged by a horde of mutated creatures. In a dramatic turn of events, they find themselves cornered, leading to a frantic fight where they decapitate the infected Fred in a cable car. Meanwhile, Felix, ever self-centered, attempts to retrieve the key to escape but unwittingly opens the door, allowing an infected kangaroo and her joey to attack.
As the fight escalates, Gracie and Dan face the ultimate challenge when they encounter the amalgamated version of Fred, now fused with a giraffe and bearing the key they need. In a frantic attempt to fend off this new abomination, Dan is infected and bears down on Gracie, triggering chaos that leads Dan to fall into a sink filled with soap and water. Miraculously, he appears to be cured by the soap, igniting a flicker of hope for their survival. As conflicts continue to grow between them, Dan seizes the key, driven by a newfound cowardice to leave the zoo.
In the confines of the gift shop, Gracie orchestrates a rallying cry as she teams up with Ash, Frida, and Xavier to find a way to cure their infected friends. As Felix gets into trouble trying to secure the key, Dan arrives to save him—only to do so solely to reclaim the key. Felix attempts to convince Dan to join him in escaping to the wild, but a change of heart sees Dan relinquish the key to Felix, who barely escapes but soon faces infection himself.
With teamwork, Gracie and the surviving animals devise a plan to lure Bunny Zero and the other Gum-beasts into an enclosure, taking advantage of the chaos caused by an infected elephant that helps collapse a water tower. They try to fill the cage's moat with water to cleanse the infection, but just as they think they’ve succeeded, all Gum-beasts unify into a colossal monstrous entity controlled by Bunny Zero, leading to a desperate race against imminent destruction.
As this monstrous creature attempts to break free and spread chaos beyond the zoo walls, Poot manages to activate a snow globe amidst the rubble, miraculously reversing her infection. This sparks a realization in Gracie; the earlier fight had left the radio on, and she now understands that music is the true antidote to the virus, not merely soap and water as she had believed. Racing against time, Gracie and Poot prepare to unleash the cure, facing down the infected Felix in a harrowing confrontation. In a moment of bravery, Gracie aims to set the clock tower to 7 o’clock and activate the music while Poot distracts the menacing creature threatening to escape.
Just as she executes her plan, Gracie is unexpectedly attacked by the infected Felix, but as the released animals join their voices together, they succeed in reverting every infected creature back to their original forms. With the zoo saved, Gracie finds herself in heartfelt reunions and bonds created from adversity. As Dan prepares to leave the zoo and return to the wild, he leaves the key behind for Gracie, opening up the possibility for her to join him whenever she feels ready to venture into the unknown alongside her new friends.
