OFFICERS are picking their way through a darkened apartment in the suburbs of south Madrid, after a chilling call to the emergency services.
The furniture is smashed and spots of blood have dripped on to the floor, but this is no normal crime scene.
"Please come quick! He is in here!" the caller had pleaded, drowning out the police operator's requests for calm. "He is here!"
Veronica, the new Netflix film being billed as the scariest of the year, starts with that chilling scene, set in the summer of 1991.
A spine-tingling horror, it tells the story of a young girl who becomes overwhelmed by a terrifying supernatural force after playing with a Ouija board.
So far it’s standard movie fare then - except this one, as the opening credits make clear, is based on a true story. And it’s one that is arguably even creepier than the stuff we see unfolding on the screen.Spanish TV report goes inside the real house behind horror film Veronica
Known as the "Vallecas" case after the area in which it unfolded, the events which took place in a small flat, 8 Luis Marín, in the working class Madrid suburb led to the production of the only police report in the country which is said to be stamped "unexplained".
Later, the senior police officer involved in the investigation would describe what he saw as "horrendous", while two of his colleagues were so panicked by what they witnessed in the flat that they had to leave moments after they entered.
That case also centred on a teenage girl, though her name was not Veronica but Estafania Gutierrez Lazaro.
The eldest of four children, she died suddenly and inexplicably in August 1991, six months after playing with a Ouija board, and aged just eighteen.
The two events, her devout Catholic parents Maximo and Conception were convinced, were directly linked.
They would later tell police that their daughter and her friends had developed an interest in the occult and on occasion had dabbled in Ouija boards.
When the boyfriend of one of the group died in a tragic motorbike accident, Estafania and two of her peers decided to perform a makeshift seance at their school.
The seance was interrupted by a teacher and later, as they tried to make sense of what had befallen their daughter, Maximo and Conception claimed that both her friends and teacher had told them they had seen a strange swirling smoke enter Estefania’s nose and mouth.
Days later, their daughter began having seizures and hallucinatory visions.
Sometimes she would go into fits of wild rage, snarling and barking at her younger brothers, and on other occasions she would tell her parents that she would see shadowy people walk past her bedroom at night.
Was it some sort of psychotic episode? Estafania’s frantic parents took her to doctor after doctor, yet none could find anything physically wrong and none could give a diagnosis.
All the while, Estefania’s health progressively worsened, and her seizures became ever more frequent. She was, she told her parents, haunted day and night by hallucinations and visions.Official trailer for new Netflix horror, Veronica
Finally, amid worsening health, the teenager was admitted to Madrid’s Gregorio Marañón Hospital where, on a sweltering evening in August 1991, she died.
According to medical reports, no cause of death was given and instead Estafania's case was labelled "unexplained".
If her grieving parents hoped that was the end of the strange and disturbing events that had visited their household they were wrong: as the months rolled by the family started to experience for themselves a series of unnerving and unexplained phenomena.
Doors would slam out of nowhere, electric appliances turned on and off, the couple sensed shadowy beings in the backdrop, and a photo of their daughter unexplained burst into flames.
Finally, at dawn on November 27 1992, one event unfolded which drove a terrified Conception and her husband from their bed.
"I felt pressure on top of me but there was no-one around," she later recalled. "I said (to Mr Gutierrez) 'there’s someone here'. I then felt a paid of hands grab my feet and then grab my hand, which were uncovered by the blanket."
The terrified pair called the National Police who arrived to find the terrified couple cowering on the pavement outside their apartment block with their children.
Leading the investigation was Police Inspector Jose Pedro Negri, who to this day confides he remains shaken by a night he has never fully been able to make sense of.
In an interview given to Spanish television in 2012 to mark the twentieth anniversary of the Vallecas case, he relived the moments he arrived outside the apartment block to find a "nervous and anxious" family unable to go back in.
"They said that it had been a terrible time —that pictures had been flying off the wall, that the picture hooks were jumping out and plates were flying through the air. It was something dreadful to see," he recalled.
"I asked him why he thought it was happening and he replied that they’d had a daughter who used the Ouija board and then she was possessed and then suffered a terrible death.
"From that point on, terrible phenomena started to appear in the house."
Initially sceptical, Jose asked the family to accompany him back into the apartment.
"After all, what could I do?" he asked. "And I wasn’t on my own as two other police cars had come too, so there were six of us in total to go up.
"So we went up and he explained what had been going on, all the paraphernalia, furniture and objects strewn around the room, the picture of the daughter upside down."
Jose was still sceptical, even if it was, as he put it "the kind of stuff that makes your hair stand on end."
"It could have been them of course," he said.
The frightened couple told the police inspector that the phenomena tended to happen at quiet times, when the house was shrouded in darkness.
"I immediately told them to turn off the light," he recalls. "We were all in a tiny little living room, all of us and the family. Then from one moment to the next, a door in the sideboard slammed open violently again and again. Bang! It was awful."
Jose shouted at his colleagues to turn on the light, and immediately searched for hidden gadgets which might explain what had just unfolded.
"But there was nothing at all," he recalled. "At that point, four of my colleagues asked if they could leave because they couldn’t cope with it. So then it was just two of us."
At that point the family took the duo to one of the apartment’s two bedrooms where, they said, most of the phenomena took place.
"It was a small bedroom with twin beds," Jose recalled. "The father told us that sometimes when he and his little son were sitting on the bed, his son was picked up and thrown on to the other bed in a flying move.
"I sat down in the same bedroom to see if anything would happen. We heard a terrible scream behind us which came from a small balcony. I quickly opened the door and ran out to see if I could see anything. But there was nothing. No fallen stones. Nothing.
"It was 2.30 in the morning and the noise was dreadful."
On return to the bedroom however, he noticed two things that made his spine tingle.
"When I’d first entered the room, I noticed they had a large wooden crucifix on the wall and hanging off it was a smaller pearly crucifix like the one children get at their first holy communions. There was also a poster."
Yet in the few seconds he had been absent, something had changed. "The crucifix had been turned upside down, the little crucifix was on the floor and the poster and the door had three or four deep scratches in them as if someone had clawed through the poster and deep into the door."
There was only one word for it. "It was," Jose told the interviewer, "horrendous."
Too scared to stay there a moment longer, Máximo and Concepcion decided to move out of their home while Jose wrote up what he had witnessed in a police report - a copy of which we see flashed up at the beginning of Veronica and which, the viewer is told, the drama is based on.
Not quite of course: as Veronica’s director Paca Plaza admits, the film is just inspired by the Vallecas case, and isn't a documentary account of it.
No stranger to frightening audiences, having overseen the 2007 zombie horror REC, he says he used the story as a starting point and that the ambiguity of what’s real and what’s not is part of the attraction of his spine-tingling film.
"In Spain it’s very popular, this story, because it is, as we say in the film, the only time a police officer has said he has witnessed something paranormal - and it’s written in a report with an official police stamp and it’s really impressive when you look at it,” he said.
“But you only have to read the different newspapers to know how different reality is, depending on who’s telling it. So I knew we were going to betray the real events."
Hence in Veronica the teenage girl summons the spirits of her dead father, and events unfold over just a few days.
Back in Vallecas, meanwhile, no other strange events have been reported inside the apartment in 8 Luis Marín, although none of those who were involved in the events that unfolded there in the early nineties have ever been able to forget what they witnessed.
Little wonder that more than a quarter of a century on, it remains one of Spain’s most enduring mysteries.