Alison’s Birthday

During a Ouija session, Alison Findlay and her friends Chrissie and Maureen contact a malevolent entity. The entity claims to be Alison's father and warns of danger on Alison's 19th birthday. Moments after the séance, Chrissie is killed when a bookcase collapses onto her.

Nearly three years later, Alison returns to her hometown with her boyfriend Pete for her 19th birthday. They visit the home of Aunt Jenny and Uncle Dean, who raised her after her parents' death. The visit foreshadows a looming, supernatural danger centered on her birthday.

Alison discovers a large stone construct in the woods near her aunt and uncle's home, a mysterious monument resembling Stonehenge. Uncle Dean explains it was built by the previous owner, a history enthusiast, hinting at occult significance surrounding Alison's past.

That night, Alison is awakened by an elderly woman she does not know. Aunt Jenny identifies the visitor as Alison's 103-year-old Grandmother Thorne, a presence Alison has never met before, deepening the sense that something supernatural is at play.

Dean and Jenny dislike Pete and move to keep him away from Alison. They drug Alison and summon a false doctor who prescribes that she stay home and avoid visitors, strengthening the cult's control over her.

That night, Pete breaks into the house to rescue Alison but is stopped by the impostor doctor and by Dean, who subdue and drug both of them. Jenny and Dean then coach Alison into telling the police that Pete has been stalking her, resulting in Pete's arrest.

After Pete's bail, he and Sally investigate Alison's birth parents at the library and learn that Dean and Jenny are Celtic cult members who abducted Alison at birth for a 19:00 birth-time ritual. They suspect Mirna inhabits Grandmother Thorne.

Pete and Sally deduce Mirna will inhabit Alison's body to complete the ritual. Cult members accost Pete in an abandoned cemetery and try to kill him, but he manages to escape, confirming the imminent threat.

Pete returns to stop the ritual and finds Alison at the stone monolith with Jenny, Dean, and other family members—including Grandmother Thorne—wearing druid shawls. Alison pleads for Pete to throw the crucifix at the cultists to deter them, and they flee through the forest as the ritual progresses.

In a clearing, Pete trips and drops his gun. Alison retrieves it and reveals that Mirna has completed the soul transfer, inhabiting the young Alison's body while Alison's soul resides in Grandmother Thorne's infirm body. She then shoots Pete to death.

When police arrive, Dean, Jenny, and the now-possessed Alison (as Mirna) tell them Pete came to abduct Alison and died in a scuffle, a story the detectives accept. After the police depart, Dean, Jenny, and Alison—now Mirna—visit Grandmother Thorne in her bed, where the aged body awakens and alarms Alison as she realizes what has happened.

In the final twist, Mirna now inhabits the young Alison's body, while Alison's soul is trapped in Grandmother Thorne's 104-year-old form. The film ends with Alison screaming in horror at her aged hands, realizing the transference has left her consciousness inside an elderly body.