The morning after hearing gunshots in nearby woods, brothers Pedro and Jaime investigate and discover half the body of a man which leads them to a nearby shack, where a woman hides with her two sons. The oldest son, Uriel, has become a "Rotten" - a being possessed by an unborn demon who is awaiting physical birth. The deceased man in the woods is a "Cleaner" that the mother called for a year prior, someone who is supposed to safely kill Uriel and abort the demon before it possesses others.After authorities dismiss the Rotten as not their problem, the brothers approach the landowner Ruiz who aggressively attempts to deal with Uriel himself by disposing of the blighted Uriel, dumping him hours away. After narrowly avoiding a young boy in the road, the three men discover Uriel has somehow escaped the truck. Ruiz declares the matter resolved and returns home unconcerned. The next morning, Ruiz's wife discovers one of their goats has become possessed. Against her warning not to use guns because they help to spread the possession of the Rotted, Ruiz executes the animal and his wife promptly commits murder-suicide with an axe.The next morning, Jaime and Pedro agree to leave the town, take their family members, and escape to safety. Jaime gets their mother, while Pedro goes to the home of his ex-wife, Sabrina. This leads to an argument between himself, Sabrina and her new husband, Leonardo, when Pedro tries to collect his two children. While they are distracted by the argument, the family dog who, previously licked Pedro's demon-mucked clothes, savagely attacks Leonardo and Sabrina's daughter and drags her outside. Leonardo and Pedro chase the dog and the former shoots the dog. Pedro returns to Sabrina but sees her daughter is back unharmed and threatening Sabrina, so Pedro steals their car. As Pedro drives away with his sons, he witnesses Leonardo crash his car into Sabrina as their daughter dances.After Pedro picks up Jaime and their mother, the assembled family leaves town and arrives at the house of Mirta, a former Cleaner and friend of Jaime, who invites them to stay overnight. Mirta warns Jaime about Pedro's autistic son as exhibiting signs of possession which Jaime dismisses. The possessed corpse of Sabrina kidnaps her youngest son and Mirta advises that Jaime chase after her while she and Pedro search for Uriel to end the demonic plague. While seeking out Sabrina, Jaime discovers she has killed the child and runs her over in a fit of emotion. In doing this, he collides with a tree. Grandma stays at Mirta's house and waits with her oldest grandson who returns to the house, now speaking clearly and without impediment.Pedro and Mirta's search leads them to a schoolhouse filled with possessed children who boldly lie to the pair in order to exacerbate the demonic birth. The pair find Uriel under the stage in the small auditorium and Pedro tries to properly unearth him as Mirta sets up the demon killing equipment. Losing his patience and believing one of the children's lies about a fire axe nearby that might help, Pedro runs to the office while Mirta screams to not leave her. While he is away, the children trap Pedro, kill Mirta and dismantle the equipment. Enraged, Pedro beats Uriel to death with a piece of the broken equipment but is too late to intercept the birth. The demon inside Uriel is born soon after, shedding his corpse and presenting itself to a defeated Pedro. After taunting Pedro by sparing him, the newly born demon walks out into the morning sun followed by the children.The two brothers return to Mirta's separately and after collecting the remaining son, head back to their own home. At the shed, Uriel's possessed brother tells him he killed the original Cleaner four days ago, devouring him. He also reveals he did the same to his mother the night before and alludes that his and Pedro's mother has suffered the same fate. Pedro returns inside and feeds his son ice cream but he begins choking. While Pedro helps him, he discovers he's choking on his mother's hair and that his son is possessed as well, having tricked him under the veil of his autism. Pedro runs outside and collapses in grief, having lost everyone but his brother. IMDb