Indie filmmaker David Lowery has diversified his portfolio like few others in the last few years. On top of that he’s been working at an enormously fast clip. 2012’s “Ain’t Them Bodies Saints” with Casey Affleck and Rooney Mara put him on the map with a Terrence Malick-like lovers-on-the-run tale, and he quickly switched things up, following up the Sundance indie with a big budget, live-action adaptation of “Pete’s Dragon” for Disney. He’s shaken things up yet again for his latest film, “A Ghost Story.” An experimental film shot on the fly, without the knowledge of their agents, Lowery’s sublime ghost movie reteams him with his “Ain’t Them Bodies Saints” leads, Mara and Affleck, to create a truly unique film.

READ MORE: ‘A Ghost Story’ Starring Rooney Mara & Casey Affleck Weaves A Mesmerizing, Fascinating Tale [Review]

In every regard, it’s an extremely well-accomplished movie, but every step of the way was a gamble. It’s a movie that shouldn’t work, featuring a character wearing a silly-looking ghost sheet on top of his head. And Lowery was well aware he might have a disaster on his hands that he’d have to scrap.

READ MORE: Essentials: 20 Of the Best Ghost Films

Fortunately, despite being laughable on paper, “A Ghost Story” is anything but. It’s a profoundly affecting meditation on love, loss and the unfathomable expanse of time. It’s both heady and existential, but also deeply emotional. It’s nothing short of a miraculous cinematic experience, and it’s one of the best movies of the year.

I sat down with Lowery to discuss the mechanics of making ghosts, pondering death, and his next film, “The Old Man And The Gun” starring Robert Redford and once again, Casey Affleck, which he describes, perhaps uncharacteristically knowing his work, as a comedy.

Casey Affleck in A Ghost Story

I keep saying this: this movie shouldn’t work. It’s about a bed sheet wearing ghost contemplating existence.
I never had any expectations for it. I didn’t know if it was a movie that anyone was going to see. I didn’t know if it would be a movie I’d need to bury or an embarrassment to everyone. I was fully prepared for it to fail and not work. When you’re operating on that level that when it proves to be the opposite, it’s hard to wrap your head around it.

I keep thinking about what the movie is like without editing, sound and music and how hard that must have been.
Every day of the shoot I was convinced that it wasn’t working. I had an idea in my head that worked and then when I wrote the script I was further convinced it worked as envisioned and then we started and all my confidence went right out the window.

It wasn’t until a few months before Sundance that we had a cut of the film that hinted to me that we might be able to pull it off, but up until then, I was seeing all the clunkiness, and early on, on a shot by shot level, the movie wasn’t working at all.

You didn’t test the ghost and how it looked?
We did a little, but we had to figure out how to execute it and we were figuring it out as we shot it. The early stages of production were trial by fire where we were learning how to make the ghost work as we shot it. There was a day or two of quick test shoots and there’s one or two shots in the final film, but what they reveal is an idea not fully formed.

You had different iterations of the ghosts then?
Yes, it was constantly evolving, really. But in the early days, it was obvious that a bed sheet over someone’s head would just not work. Eventually, we contrapted a helmet that you would wear under the sheet that would keep the shape and the eyes symmetrical. Like one version was great for standing still, but as soon as he started to walk he would trip over the sheet. It looked like a deconstructed wedding dress under the sheet.

Was Casey Affleck under the sheet the whole time?
He was under the sheet the whole time. The only time he wasn’t was when we went back and did some reshoots and pickups and he couldn’t be there for those. We wanted Casey to be under the sheet so his performance would come through in a profound and recognizable way, but it looked too much like a human with a sheet over their head until we got the costume right. So at the end of the day, I think it could have been anyone underneath because it was a very mechanical acting, actually, but Casey always wanted it to be him and he was very possessive of it, and he was disappointed when it couldn’t be him, but it could have been anyone and I don’t mean that at all as a slight to him as he does some great, non-ghost acting in the film. But the suit required an extreme amount of stamina and the ability to stand absolutely still and then move very, very slowly [laughs].