Spain, 19th century. In a small coastal village, Olalla and her family prepare to live a very special night, during which it is mandatory to comply with a single rule: no light must remain on.

An octogenarian named Manuel falls into a state of dementia after the sudden suicide of his wife, sparking a series of paranormal events that will put his family’s lives at risk.

Four people traveling in a van run over a lone woman while she is walking in the dark down a country road. After loading her into the vehicle to take her to the nearest hospital, they notice that she is behaving rather strangely. The occupants of the van soon realise that the time has come to fight for their lives, and together they agree on one very simple rule: "do not sit next to her."

Based on real events. The 1990s. Two friends from Móstoles set out on their first trip together to Valencia, unaware that their adventure will turn into a living hell and that they will be about to become two more names on a macabre list, and part of one of the darkest chapters in the history of this country.