A zookeeper named Jim and his colleagues watch the CCTV footage of an incident over and over again, but nobody can explain it. In November, when the incident occurs, the zoo is mostly empty. Jim is sitting in the observation tower watching the visitors on footage. He sees a boy who looks like a teenager standing in front of the lion enclosure for a long time. He decides to go take a look, because sometimes visitors come who try to commit suicide or poison the animals, among other behavior. When he gets to the lion enclosure, the boy is starting to climb over the fences into the enclosure and other visitors are yelling. The boy does not seem nervous or hurried. He stands in front of the lions and starts yelling at them in a strange language nobody is able to identify. The boy takes his clothes off, beginning to scream in the language and jumps up and down. The lions snarl and roar. The boy does not listen to the zookeepers who call to him. All of the lions run at the boy, and zookeepers try to shoot them but miss. All of a sudden, all of the floodlights go out. A visitor takes a picture with flash that shows all of the lions in a heap on the spot where the boy was. When the emergency lights come on, the lions are in various corners of the den, and the boy is gone. There is an investigation, and Jim notices that the boy never entered the zoo on the cameras; he just appeared. He is never found, and there is not evidence of the lions eating him. The incident is forgotten, but the lions start acting strangely. A zookeeper sees a large male lion out of its cage on surveillance. He calls an emergency, and the police come. When they check the lion cage, all of the lions are accounted for and are in the cage, and they do not find another lion on site. The lions are acting in a way that creeps Jim out, and they are not acting like caged animals. In the following months, lions are seen outside of their compound on five occasions even though they would have to navigate multiple spiked fences. There is footage of one occasion, and even though the lion is next to the zebras, they do not run away. However, when the zookeepers come, they all run. All of the animals start acting hostile towards humans. Extra guards are hired, but they are not zookeepers and they purposely taunt the animals. One day in April, two of the guards are making fun of the baboons, close to the fence. There is a commotion on the camera, and the baboons start hooting. One of the guards steps in to help his friend, whose face has been mostly ripped off. Then, the baboons stop hooting and just watch. The guard reaches for his walkie-talkie and turns, then sees something in the trees that makes him start running. Jim and another zookeeper go to assist him. Manoj, one of the zookeepers, watches from the observation tower and tells Jim and his coworker on the radio that the man is running to an underground tunnel, where they keep nocturnal animals, that does not have cameras. They hear screams from the tunnel that then stop abruptly. Jim and his coworker go in the tunnel, which smells horrible. The bats, lizards, and insects simply stare at them. They find the guard's body, which there is not much left of.
The zoo gets shut down after this incident. Before the zoo is fully closed, the zookeepers stay to look after the animals before they are shipped off to different zoos across the country. The zookeepers only walk around the zoo once or twice a day, because they are scared. Once it gets dark out, animals of all different species wander the zoo together. There has been a shift in power, and the bars are there to protect the zookeepers now instead of enclose the animals. Manoj thinks that the behavioral shift was volitional, and that the animals have gained self-awareness. Jim thinks about how frightening this idea is, since the animals will all get shipped to different zoos and may pass on their new behavior to other animals. Jim thinks that nothing is safe in a cage anymore.