On Halloween, medical students Jorge, Servando Manzetti and Oscar lure their friend Pedro, Andrés García Jr., his girlfriend Lena, Erika Buenfil, and their girlfriends Olivia and Mariana, Edna Bolkan and Jacqueline Castro, into breaking into an abandoned house for a Halloween party.
Meanwhile, Dr. Cardan, Hugo Stiglitz, learns that Devlon, José Gómez Parcero, a serial killer obsessed with Satan, escaped from a psychiatric hospital and was killed in the process. Cardan seeks a judge's clearance to have Devlon's body cremated.
In the attic, Jorge uncovers Devlon's book of Satanic incantations and suggests stealing a corpse to attempt a return from the dead. The group breaks into the university hospital morgue and steals Devlon's corpse, unaware that it is the killer's.
Cardan arrives at the morgue to cremate Devlon's body, but the youths have already taken it. They transport Devlon's body to a cemetery where Jorge performs a ritual, frightening everyone and causing them to flee the cemetery and return to the house, unaware that they have resurrected Devlon.
Back at the house, Mariana is attacked and killed on the porch. Oscar finds her body outside, and is also attacked and killed. Olivia goes to investigate the noise outside, finds Oscar's corpse, and flees into the house in hysterics. Devlon proceeds to kill Jorge and disembowel Olivia, before stabbing Lena to death upstairs. Pedro witnesses Lena's death through the window from outside, and arms himself with a hatchet, which begins to levitate on its own before bludgeoning him to death.
Meanwhile, Tony, Eduardo Capetillo, visits the cemetery along with two classmates, Usi Usi Velasco and Cesar César Velasco, along with two younger neighbors, Anita María Rebeca and Raúl César Adrian Sanchez, who have been trick-or-treating. They encounter Devlon's tomb bursting into flames, which sends them running in fear. They seek shelter in the abandoned house, where they find the multiple dead bodies. Devlon appears and chases the children upstairs. Tony arms himself with the hatchet from Pedro's head, and they flee the house. As they run through the cemetery, various corpses—each awoken by Devlon—begin to rise from their graves and attack the children.
Cardan, who has gone to search Devlon's house, finds the children in the cemetery and attempts to save them. Cardan becomes pinned under a fallen branch and injures his leg. He tells the children they must burn Devlon's book of incantations to stop the zombies, and sends them back to the house while he wards off the undead with a crucifix. The children retrieve the book as the zombies, with Devlon at the helm, descend upon the house. Cardan arrives to save them, and wards off the violent Devlon. Usi throws the book into the fireplace, causing all of the undead to burst into flames. Shortly after, police, who have been searching for the missing children, come to their rescue. In the last scene, Cardan brings the charred remains of the book to the altar in the attic, now apparently possessed by Devlon himself.
