The film opens in medias res, with emergency services racing to answer a panicked call from a young girl on June 15, 1991. She screams that something is coming to get her brother before the line cuts off, and the scene then rewinds three days.
In Vallecas, Madrid, Verónica Sandra Escacena is a 15-year-old who lives with her family. After her father dies, her mother works long hours to support everyone, leaving Verónica in charge of her younger siblings: twins Lucía Bruna González and Irene Claudia Placer, and Antoñito Iván Chavero. The daily weight of caretaking sits heavily on her shoulders, shaping how she navigates school, friendships, and the strange occurrences that begin to pile up around her.
On the day of the 1991 solar eclipse, a teacher explains how some ancient cultures used eclipses to stage human sacrifices and summon dark spirits. Later, in the school basement, Verónica, with her friends Rosa Ángela Fabián and Diana Carla Campra, conducts a séance using a Ouija board. Verónica hopes to reach out to her late father, while Diana tries to contact her boyfriend who died in a motorcycle accident. The glass cup used on the board grows exceptionally hot, and Rosa and Diana pull their hands back. As the eclipse occurs, the cup shatters, cutting Verónica’s finger and letting her blood drip onto the board. Verónica becomes unresponsive, whispering something she won’t reveal and then emitting a chilling demonic scream. When she wakes, she’s in the school nurse’s office, who suggests she may have fainted from iron deficiency.
Paranormal occurrences begin to pepper Verónica’s life, and her friends start avoiding her. Back in the basement, she encounters the elderly blind nun nicknamed Hermana Muerte. The nun, portrayed by Consuelo Trujillo, explains that the séance has attached a dark spirit to Verónica and attempts—but fails—to force it to leave. Verónica also draws protective Viking symbols, only for the demon to destroy them. In a terrifying moment, she intervenes when the spirit chokingly reaches for Lucía, only to realize she herself is the one who is choking her sister.
Verónica wakes to discover she has begun her first period, and while she cleans the blood from her mattress, she notices burn marks on the underside. She also finds, on each of the kids’ mattresses, a large burn mark in the shape of a human body. Hermana Muerte shares a painful family truth: she used to see dark spirits as a child and, in a desperate bid to escape them, blinded herself—an act she now regards as a misstep. Verónica reads in an occult magazine that the spirits can be forced to leave if she makes amends for what she did wrong and, crucially, says goodbye to the spirit at the end of a séance. She convinces herself to try another séance, but Rosa and Diana refuse to participate. Rosa then reveals that at the séance Verónica whispered she would die in three days.
Desperation drives Verónica to hold a séance with her siblings. Antoñito is tasked with drawing protective symbols on the walls, but he copies the invocation symbols by mistake. As they sit through the ritual, they must repeatedly sing a melody and choose the advertising jingle for “Centella,” the only song they all know. When Verónica commands the spirit to say goodbye, it refuses. She calls the police and escapes with her siblings, only to realize that she is not actually holding Antoñito—he’s hidden in a closet. She finds him, but he won’t go with her. Standing before a mirror, Verónica sees the demon she’s been hosting, understanding that she has been possessed and harming her siblings through its control. In a desperate bid to end the possession, she attempts to slit her own throat, but the demon thwarts her. The police arrive to find Verónica attacked by an unseen force, and she passes out as medics carry her and Antoñito away. A shaken detective watches as a photograph of Verónica in the house suddenly catches fire, and he is informed that she has died.
In the official report, the detective notes unexplained paranormal activity within the home. The film closes by noting that it is based on the true events of Spain’s first police report documenting witnessed paranormal activity, underscoring the chilling thin line between belief and reality.
