It was a challenge that didn’t stop actor - now first-time director - Kieran Darcy-Smith when he shot a large segment of his new film Wish You Were Here, in Cambodia.

‘‘The entire experience was challenging in the extreme and I absolutely loved it,’’ he says sitting crossed-legged in an oversized chair in Canberra. ‘‘I’ve never felt more alive.’’

Written by married couple Darcy-Smith and Felicity Price, the film tells the story of four friends who take a relaxed, alternative holiday to the beautiful beaches of southern Cambodia. One night, with a full-moon party in full swing, one of them goes missing. The other three return to Australia where the fallout begins, stretching relationships to breaking point as the memories of what happened are slowly pieced together.

The acting/writing/directing couple see the film as having two complimentary halves.

‘‘The mystery was always there from the beginning of the writing process,’’ explains Price, ‘‘and it’s critical for the audience - it’s what turns the page. But the other side of the story is about how relationships are put under pressure.’’

Price plays the role of Alice in the film and it’s her marriage to Dave (Joel Edgerton) that starts to crack as the mystery unfolds.

With both Darcy-Smith and Price coming to the film with acting backgrounds, you can be assured that the script was developed around the characters.

‘‘We very much put ourselves in the shoes of the characters,’’ Darcy-Smith says. ‘‘We explored our take on this world and, like the characters themselves, we have two small children. We wanted to open up the idea of people with small children suddenly having to grow up and deal with parenthood and a crisis.

‘‘While writing we put ourselves in the scenes all the time, so I would always ask Felicity, ’What would you do if you were Alice?’ It offered such fertile ground for us as writers.’’

The film was chosen to open this year’s Sundance Film Festival, an occasion that Darcy-Smith describes as ‘‘excruciating’’, but one that resulted in some excellent international press for the film, which its makers hope will follow the international success of Animal Kingdom. It’s been a passion project for the director who has been obsessed for years with the idea of an unexplained disappearance.

‘‘Think about the extraordinary vacuum that opens up for those left behind,’’ he says. ‘‘The unknown, the possibilities, and the notion of truth. The narrative plays out from shifting points of view as we track one man’s suppression of the truth, the repercussions of his decisions and the necessity, for everyone, for the truth to come out into the open. And so ’truth’ became a directorial by-word. My absolute priority, from script to screen, is truth.’’

But Darcy-Smith admits that early versions of the screenplay left the mystery unresolved - something that was changed as the writing progressed and as he and Price realised the extent to which the viewer would buy into the mystery.

‘‘People have been so responsive to the mystery in screenings so far,’’ Price says.

‘‘They invest in Alice and track all the little things that have happened to Dave - things that are revealed little by little.’’

Darcy-Smith chips in with an explanation of how they structured the story: ‘‘We smashed the structure up so that people would initially be wary of Dave and his role in what had gone wrong, but also intuitively sense that he was a good man. That’s what makes him interesting.’’

How Darcy-Smith got Joel Edgerton to play the part of Dave is a story in its own right. The two have been friends for many years, and Darcy-Smith kept asking Edgerton for advice about who could play the lead as the story was developed.

Then one night, Darcy-Smith asked him to come and help with a casting session.

‘‘By that stage Joel had read every draft of the script,’’ Darcy-Smith says. ‘‘We’d been mates for a hundred years and so while we were looking at pictures of other actors he simply pulled me up and asked, ’Dude, have you ever thought about offering it to me?’ Once I’d picked myself up off the floor, we were off and running. The film seemed to finance itself very quickly after that.’’

Filming in Cambodia - with two small children in tow - also had its share of stories. But Darcy-Smith remembers the adventure fondly.

‘‘We were shooting in authentic locations, in some of the sketchiest parts of the country and more often than not working with non-actors. Our crew spoke very little English, their equipment was, at best, antiquated and second-rate and our locations were being demolished before our eyes. Our days were long, chaotic, hot, plagued by illness, exhaustion and gear setbacks. I fell neck-deep into a sewer on day one and that was one of the easy days. Our final night in the country I missed the wrap party as I was holed up in my hotel vomiting.’’

It hasn’t dampened his enthusiasm for doing it again. He and Price are developing two new film ideas to take to south-east Asia.

Wish You Were Here opens nationally on April 25.