Perhaps best known for his cult vampire series Ultraviolet, Joe Ahearne’s latest project, Apparitions, stars Martin Shaw as an exorcist priest investigating all things paranormal. Marie O’Regan caught up with Ahearne to talk about miracles and demons.

What was the initial inspiration behind Apparitions? I read it was because Martin Shaw wanted to play an exorcist.

That’s the one. He suggested the idea.

Was it easy to research the methodology for the Congregation for Causes of Saints, was the information easily available?

Pretty much. I read books on them and kind of did the usual thing, spoke to a few people. The exorcism aspect was a bit more difficult because the church doesn’t like to talk about it as much.

That’s what I was wondering, if there was a lack of cooperation there?

Not so much a lack of cooperation, just less of it and therefore less people who know about it, and therefore – particularly in this country – there’s not so much of it. Most people’s experience of exorcism over here is throwing some holy water around, houses that have got a bit of a strange energy about them. Lots of priests have done that kind of exorcism, not many people have dealt with exorcised people over here.

Apparitions went very quickly from being a two-parter to being commissioned as a six-part series; how did that happen?

I think there was always the intention to do the series, then they decided to pilot it. And I think once they saw the first episode they thought, ‘No, actually…’ They were confident enough to go straight to the series.

Will there be a second series or was there a definite end point?

No, there’s scope for more – if enough people watch it, I suppose. If it strikes a chord.

Was there much restriction on how you could treat the subject of exorcism for a TV audience, on how dark you could go?

Not really, surprisingly, I thought there would be. It was Jane Tranter who approached me and the words she used were ‘The Exorcist’ and ‘terrifying’. So I took her at her word; I’ve seen The Exorcist many times and I tried to make it as scary as I could.

The first episode hasn’t been censored and we’ve got scenes of extreme violence and extreme darkness, so it’s not just psychological horror where people are being a bit nasty to each other. We have – although I’ve said it’s not like Strange – these stand out moments of extreme horror. But I have to soft pedal a bit on it. What I’m hoping is if you’re honest with the stories and you make it interesting and intelligent, people will accept the violence and the dark stuff, because it’s within the context of a whole world that you believe, which you do feel has some integrity. It’s not just cheap shocks for the sake of it.

Does the show deal with the duality of miracles, whether they’re actually from God or could perhaps be a trick from Satan?

Yes, the first episode is the starting point of the story, which is that Father Jacob works for the Congregation for the Causes of Saints, authenticating miracles. So if he goes to see a miracle, in most cases it’ll be fraud or delusion or mental illness. Very, very occasionally it’ll be the presence of God; and also very occasionally it’ll be the presence of Satan. A Satanic miracle. And that’s when Father Jacob might do an exorcism.

So he does exorcisms very rarely in this job normally, but when the series kicks off, his mentor, who was the Chief Exorcist of Rome, is trying to encourage him to do it more full time, if you like, so that’s the exposition.

In the first story Jacob is trying to locate the second miracle of Mother Teresa – Mother Teresa has already had her first miracle, and she’s been beatified, and he’s looking for the second Miracle that allows her to become a Saint. And the miracle that he’s putting forward, if you like, is a young priest who was cured of leprosy when he was a teenager by praying to Mother Teresa.

During the course of that first story the young priest is tormented by demons who say that his skin, his new skin, was given to him not by God but by Satan. And so again, is that a Satanic miracle or a Godly miracle?

Wasn’t Mother Teresa herself exorcised at one point?

Yes, that’s how our series starts – we show her being exorcised in Calcutta in 1997, which is on record. You think it’d be a much more well known fact, that’s part of what the research picked up on: how could someone as holy as that and is a saint be exorcised? And when you look into it you find out that the church wasn’t saying that she was possessed, but she was being attacked by demons. That’s what the Archbishop of Calcutta thought and so he called in an Exorcist. That’s how our story starts off.

So would you say the show takes the religious standpoint or more of secular view? Or does it just have an open mind?

Well, the story is a bit like Ultraviolet – you have to say vampires exist otherwise you wouldn’t have a story. With this you have to say demons exist and they’re in Hell, and everything else is open to interpretation. I’m an atheist, so I’m kind of on the demons’ side in a way; the demons are in Hell because they rebelled against God and won’t obey him. Well, why should they be in Hell for that? That’s the demons’ argument.

So, the demons are committing terrible crimes, but they’re saying, “We’re in a place of eternal and infinite punishment and suffering and, until you share our suffering, you won’t understand that you’re worshipping an unjust God.”

It’s a bit like the terrorist argument: ‘there’s terrible suffering in Iraq or Palestine, we’re going to blow up part of your city so you can understand the suffering that we’re in’. So that’s the paradigm that we’re in.

Apparitions begins on BBC One on 13 November 2008.