The strange case of Father Malachi Martin, the Kerry priest who stars in Netflix's new documentary

We may live in a largely post-religious world, but for most of us, there's something enduringly compelling about things like Ouija boards, haunted houses, demonic possession and exorcisms. 

While the rational brain insists none of this is possible, some deeper, more elemental part of the psyche still feels that tickle of dread from time to time.

Hostage to the Devil, which launches on Netflix this weekend, examines the work of Father Malachi Martin, a Kerryman who claimed to have performed several exorcisms in America and still, 17 years after his death, remains something of a cult figure (no pun intended).

The film was made by Dublin-based Underground Films and Causeway Pictures in Belfast. 

The trailer promises a dramatic, unnerving story of faith, terror and tortured souls - though whether "soul" is meant metaphorically or literally is up to the viewer to decide.

As Underground's Rachel Lysaght, who produced the documentary, points out, "People have a fascination with this stuff. I think it's what we can't explain or understand. Nobody can prove, without a shadow of a doubt, that the devil is real or not, so it becomes this continuing question and investigation. Stories of exorcism obviously speak to something in people the world over, of all different faiths."

Though the documentary focuses on Malachi Martin's Stateside career as an exorcist, his entire life was quite incredible, more the stuff of fiction than reality. (Rachel reckons, "Malachi's life would deserve a multi-part series, it's pretty amazing.")

Born in Ballylongford in 1921, he became a Jesuit priest, did a doctorate in archaeology and Semitic languages in Belgium's Louvain University, worked on the famous Dead Sea scrolls, participated in archaeological digs in Egypt and served as private secretary to a Vatican cardinal, among many other achievements.

In 1965, unhappy with certain aspects of Vatican 2, Malachi left Rome and the priesthood, moving to New York where he worked as a taxi driver, waiter and writer. He became a US citizen and published 17 books, both fictional and not, including Hostage to the Devil in 1976, which described five "real" exorcisms he claimed to have carried out in America.

In time, Rachel says, he "became this iconic person within the paranormal world. Many of the famous people in that field, such as Lorraine Warren, who was involved in The Conjuring, worked with Malachi".

When Rachel first discussed this project two years ago with Chris Patterson and Paddy McCarney of Causeway Pictures, they'd been doing a lot of research on Malachi, and uncovered "a treasure-trove" of audio recordings with him - about 24 hours' worth.

She goes on: "This was primarily from radio interviews on a cult paranormal-themed radio show, Coast to Coast. From 1995 to 1998 Malachi took part, and listeners would phone in and talk to him about things that had been disturbing them, say if they thought there was sort of satanic activity happening.

"Malachi was frequently critical of the Catholic Church, and spoke of a lack of support for those who felt they were being inflicted by something demonic. Even now, every Halloween, the show plays some of those interviews and gets over a million listeners. It really struck a chord."

Malachi's first 'exorcism' took place in Egypt in the 1950s, though the film concentrates on his actions from the mid-1960s. Hostage to the Devil doesn't include interviews with survivors of exorcism - primarily because they're hard to find and reluctant to go on camera, Rachel explains - but there is footage of alleged exorcisms.

Essentially, the film asks: was Malachi Martin, as one contributor puts it, "a warrior for Christ", or was he a fantasist and charlatan? On the one hand, people who sought his assistance did so because they truly believed he could help; many who worked with Malachi speak glowingly of him.

On the other hand, there are some critics. "He sometimes rubbed people up the wrong way," Rachel says, "William Peter Blatty (author of the original Exorcist novel) wrote a tirade against Malachi, saying his 1976 book was fantasy, and he was just trying to cash in."

Malachi aside, there's also the core question of whether any of this is real. The filmmakers speak to a psychoanalyst who says she often came across people charged with a crime, who claimed the devil had made them do it, in a bid to avoid prison. It might all be mental illness, hallucination, schizophrenia, a myriad of other psychiatric conditions - or outright chicanery.

That psychoanalyst, Rachel notes, "said you have to question, question, question everything, and always remain a sceptic. You need to rule things out." But, she adds, sometimes you also have to rule things in.

"Our film interrogates the question: is the devil real? I would be sceptical myself, and nine times out of 10 there's some other explanation for these strange goings-on. But I used to have a much firmer position, on what I thought was true or not true.

"Having spent time with these different people, knowing they have integrity and hearing their stories about paranormal experiences - I have more questions now. I recognise now that there are more areas of grey than black-and-white.

"As Shakespeare wrote, 'there are more things in heaven and earth than are dreamt of in your philosophy'. And I'm sure I'm not alone.

"When you scratch the surface with people - around Halloween, say, or Friday the 13th - everyone seems to have some personal ghost story to tell, or someone they heard of messing with a Ouija board and it went wrong. These stories are captivating. They speak to something within us and our human experience. We know there are things that can't be explained and this draws us in."

Hostage to the Devil debuts on Netflix this Sunday, January 15