A desperate father, Mike Lawford, embarks on a frantic quest to locate his son, Charlie, after he goes missing during a Halloween carnival. As nearly a year passes without any leads, both Mike and his wife, Kristen, begin experiencing eerie occurrences that seem to connect them to Charlie from the beyond. One day, Mike catches a glimpse of his son on a bus, but when he rushes to catch it, he finds the bus empty. His only clue is a haunting phrase spray-painted on a nearby wall: "pay the ghost," which echoes words Charlie spoke before his disappearance.
Curious and desperate for answers, Mike investigates further, discovering a rundown building where he encounters homeless individuals. Amidst their conversations, he hears chilling screams of a woman, which the blind homeless man warns him about, stating that these sounds emerge each year, preceding Halloween. The man leads him to a wall etched with similar cryptic phrases, drawing Mike's attention. Unbeknownst to him, this moment marks a shift into another realm as a demonic figure briefly manifests, sending Mike fleeing in trepidation.
Meanwhile, Kristen becomes unnerved when she notices their son's scooter moving on its own. As the couple’s tension grows, the lights in their home flicker out, prompting Mike to peer outside. To his horror, he sees the spectral figures of three children brutally burned at the stake, signaling the very real danger that looms over them. They call upon a psychic for help, who inadvertently stumbles into a realm of horror when she declares, > "It's here... it has all the children." Soon after, she suffers a terrifying fate, her internal organs burned to ash.
In a disorienting twist, Mike hears Charlie’s voice emanating from Kristen, who is found in distress, engaging in self-harm. Upon finding a mysterious symbol on her body, they learn about an ancient Celtic Halloween ritual. A friend, Hannah, reveals the dark history of a widow who was wrongfully accused of witchcraft, leading to her execution alongside her children. Every Halloween since, this mourning spirit has abducted three living children to exact her revenge, trapping them in a parallel world.
As desperation mounts, Mike and Kristen find themselves under siege from supernatural forces, suffering injuries from a swarm of ominous black vultures. Tragedy strikes when Hannah is killed, leaving Mike to confront a pivotal moment. He seeks the help of the blind homeless man once more, trading his watch for guidance to reclaim his son. The man warns him that he has until midnight on Halloween to rescue Charlie, or risk being ensnared eternally.
Mike's harrowing journey takes him to a lonely cabin, where he discovers hundreds of children’s souls confined over the centuries during Halloween. Finally locating Charlie along with two other children, they attempt to flee but are met by the wrathful ghost widow. Just when hope seems lost, the spirits of the other children rally to protect Mike, overpowering the ghost and freeing themselves at last.
As dawn breaks, Mike and Charlie return home, greeted by an unsuspecting Kristen, who learns that her son has been shielded from the trauma of his ordeal. However, a dark omen lingers when a black vulture makes a haunting exit from their lives. In a chilling mid-credit scene, the narrative circles back as Hannah’s lifeless body stirs, now possessed by an unknown evil.
