MARTY STALKER looks a little embarrassed. What started as a joke about the cliché of the “cursed” horror movie shoot has taken a decidedly odd turn as Stalker, the director of new exorcism documentary, Hostage To The Devil, struggles to explain the unnerving experiences he had while making his film.

“When I was reviewing the footage of Robert walking towards the house, I accidentally sped it up and at that speed, you could see this big shadow in the forest behind him. It just literally crept along and followed him as far as the house,” Stalker ruffles his hair uneasily. “It was really creepy and strange.”

Hostage To The Devil, just released on Netflix, documents the life and work of a purported real-life exorcist, Irish former Jesuit priest Malachi Martin, who may have been the inspiration for the classic horror The Exorcist.

Mysterious childlike footsteps and the sound of a little girl crying, even though his own daughters were safely occupied in a different part of the house, shadows flickering in his footage and camera equipment that stopped working for no reason; Stalker, an ex-military Liverpudlian who now lives in Belfast, seems to have run the gamut of creepy happenings during his five-year immersion in a distinctly Catholic world of supernatural beliefs. He managed to remain pragmatic throughout.

“I just kept reminding myself that I was there on someone else’s money and that you can’t just get sucked into this paranormal supernatural world. That’s the military man in me: Just plough through, objective complete,” he says.

Including real footage of exorcisms being performed and interviews with priests who perform them, the unsettling documentary explores our age-old human fear of and belief in demonic possession through the story of Kerry priest Malachi Martin.

Stalker, the son of a Church of England vicar, is hesitant about revealing whether he himself believes in exorcism as a true phenomenon.

“I’m getting asked that question all the time,” he sighs. “I would say yes. I’m more sceptical now than I was before we made the film, and certainly I’m a lot more educated than I was, but yes, I do believe in it.”

Whether we view tales of possession through a rationalist lens, as the relic of an era when medical science couldn’t explain physical conditions like epilepsy, or whether we believe in de facto possession, Martin’s life is fascinating and worth exploring. Described in the film both as “a warrior for God” and as “a liar, scoundrel and cheat”, there are verifiable facts about his life that lend themselves to cinema.

Born in Ballylongford in Co Kerry, Martin joined the Jesuits following his studies, where he specialised in ancient languages. The Jesuit order has confirmed that he worked on translating the Dead Sea Scrolls and on archaeological digs in Cairo in the 1950s. Rising through the ranks, he became adviser to Cardinal Bea in Rome and accompanied Pope John XXIII on several visits.

Following Vatican II, concerned at what he perceived as the corruption of his own order and the wider church, he received dispensation from his Jesuit vows and lived as a lay person in New York, where he wrote prolifically and made ends meet with jobs in the service and retail industries.

But Martin was a controversial figure. The Exorcist was released in 1973 with much accompanying hype; it’s still hailed as both one of the scariest films ever made, and the highest grossing horror movie of all time. Sceptics say that Martin’s 1976 book, Hostage To The Devil: The Possession and Exorcism of Five Contemporary Americans, doesn’t prove Martin as the inspiration for The Exorcist, rather that he cashed in on the phenomenal success of the film and the resulting interest in all things unholy.

William Peter Blatty, the recently deceased author of the novel on which The Exorcist was based, denied Martin was an inspiration, despite some marked similarities between the character of Father Merrin, played by Max Von Sydow in the movie, and Martin.

“But there are parallels,” Stalker says. “It’s unorthodox to see a priest in that role of both archaeologist and exorcist.”

After the publication of his book, on the east coast of America, Martin became the go-to guest for media discussions of exorcism. He featured in televised interviews and guest appearances with paranormal investigator Lorraine Warren, whose own career inspired numerous spooky cinematic offerings such as The Conjuring and The Amityville Horror.

“Did he ride the wave of The Exorcist’s success? Yes,” Stalker says. “I don’t think his intention was to profit, but he was a great writer and storyteller. Was he a fantasist, a sociopath, a philanderer? Some audiences like those questions answered for them, but we’ve only scratched the surface with this documentary. I believe you’re going to see a lot more content generated around this man.”

Hostage To The Devil was shot on a budget of €250,000, supported by the Irish Film Board and Northern Ireland Screen, and produced in Belfast by Causeway Pictures and Underground Films. Stalker’s first feature-length project, the film came about in a suitably cinematic way.

“Two of the producers were in a pub in Dublin when they were approached by a priest,” Stalker says. “He told them that they should make a film about Malachi Martin and they said, ‘Who’s he?’ and he said, ‘Go and find out.’ When I got involved, I couldn’t believe that nothing had already been made about the man.”

The acquisition of Hostage To The Devil by Netflix is a huge coup for Stalker as a first-time feature-length director. “Film directing is a craft, but also a business. Old Scratch would approve; Father Martin wouldn’t… or maybe he would.”

In making the film, Stalker spent years winning the trust of Martin’s supporters. Interviews, including long-timeformer FBI agent Robert Marro and with Ralph Sarchie, a former NYPD officer and self- professed demonologist, who authored Deliverance from Evil, which in turn became a film starring Eric Bana, interweave with the tale of Martin’s last assignment as an exorcist, involving a four-year-old girl believed to be possessed.

Martin died in 1999 from a cerebral haemorrhage following a fall in his home; to this day, his adherents claim supernatural involvement in the fall, which occurred after his encounter with the child.