Some 40,000 children have been captured, tortured, raped and turned into soldiers or sex slaves by the LRA (Lord’s Resistance Army) in southern Sudan and northern Uganda since 1986.

That’s such a staggering number – and such a foul crime – that the imagination has trouble taking it in. It’s the kind of statistic that can leave you numb at the sheer scale of the brutality and madness that led to it. What kind of future can a nation have when so many within it treat their own children worse than animals?

In 'Machine Gun Preacher,' the harrowing and inspirational new film that opens Friday with Gerard Butler and Michelle Monaghan in the starring roles, that story is told -- as is the story of one man’s determination to resist it.

The film tells the story of Sam Childers (Butler) the real life ex-biker turned preacher whose life is transformed by a trip to East Africa. Helping to repair homes destroyed by civil war, Childers is outraged to learn of the horrors faced by the region’s population and especially by their children. He decides to help them on the spot.

Since 'Machine Gun Preacher' is based very firmly on Childers’s true story, neither the script nor the actors attempt to gloss over what a maladjusted jerk Childers had been before (with the help of his wife) he turned his life around. But his dark past gives him an insight into others.

Once he was a biker and a heroin addict on the road to nowhere, and when we first meet Childers he’s coming out of prison and very likely on the fast track back to it.

But in the interval his wife Lynn (Monaghan), a former stripper, has found God and begins a process of finding a new story for herself and a new future for her family.

That spark slowly works its change on Childers too, and he eventually he finds himself working on a short mission to East Africa (he’s a home builder by trade) that completely changes his life.

Ignoring the warnings of the locals, Sam builds an orphanage where it’s most needed, directly in the middle of the territory controlled by the vicious LRA. From there Childers leads missions deep into enemy territory to free kidnapped children from their clutches, bringing peace to their lives and eventually to his own.

It’s his inability to let go, his refusal to go back to his own life and let all he’s witnessed become a story he tells his friends that makes him such a remarkable man. And his wife Lynn is cut from the same mettle.

“What was most incredible about Lynn was what a profoundly grounded person she is,” Monaghan tells the Irish Voice by phone from Los Angeles.

“It was a very hard role to play in that it led me to ignore my own instincts. The real life Lynn doesn’t allow herself to get angry and upset when I wanted to unleash, but I had to portray someone who was real and that I had to honor her by being true to that.”

Eighty percent of the events in the film are real, Monaghan confesses.

“Let’s get real, these two have gone to hell and back. She’s had a lot of sleepless nights long before he was doing God’s work,” she said.

“His history has taught her that things could be much worse than seeing him working for justice over in Sudan. The fact that these people are flawed, that they’re not perfect, I found that inspirational.”

Irish American audiences will be familiar with Monaghan for her outstanding performance as Angie Gennaro in Dennis Lehane’s Gone Baby Gone. But what they might not know is that her family hails from the town of Monaghan in Co. Monaghan (it’s her last name too, she need never get lost there).

“My parents have been and I’m ashamed to say that I haven’t yet. They’ve spent time over there and absolutely loved it,” Monaghan confesses.

“I’m proud to be Irish and I’m proud we kept the ‘G’ in our surname. I know quite a few Monaghans that got off the boat and dropped it right away. My family didn’t.”

Would she play an Irish role? “Would I? Please! To be given that kind of opportunity and acting challenge – I would probably cower in the corner a little bit and then I would come out swinging. I would love that opportunity.”

'Machine Gun Preacher' opens on Friday.