I remember when my mother was dying — or, more accurately, when I realized she was dying. My first thought was that it couldn’t be happening, because life without her wasn’t imaginable. I looked around to hit the STOP button somewhere, but there just wasn’t one. So I resigned myself to the awful fact that I was indeed going to lose her, and all I could think about was how I could fill the time I had left with her with things that were meaningful and express to her all she meant to me.

The Genius of Marian is ostensibly about filmmaker Banker White’s late grandmother, the painter Marian Steele, and his mother Pam’s desire to memorialize her work. But Marian’s art winds up playing a very small (though important) role in the film, which soon becomes a three year study of Pam’s own decline due to early-onset Alzheimer’s at the age of 61.

White was privileged to come from an artistic family that bequeathed him a wealth of documentary photographs, family films, paintings and other visual media with which to paint a portrait of his mother’s life. A beautiful woman, she had been a model and done commercial work in her youth, and maintained a career as she raised her three children. She had the life that women born in the post-WWII years were supposed to aspire to but rarely achieved — a wonderful husband, successful children, devoted friends and a graceful New England upper-middle class lifestyle that had no material wants.

Watching Pam’s inexorable mental and physical decline over the course of the film is the kind of thing we’ve seen in documentaries before, always painful but not new territory. What makes The Genius of Marian unique and extremely emotional is the filmmaker’s use of the camera to try come to terms with the loss of his mother, and tell her everything he wants to say to her in the time they have remaining — even as he watches her slip away.

It’s a really beautifully composed film and anyone who has lost a parent or loved one to the ravages of old age will be moved as they see the family members pull together to collectively cope with Pam’s decline, as well as her own personal struggle. There was one moment for me, however, that was one of the most honest and achingly painful I’ve ever seen in a film before, and I admit I had to put it on pause for a minute before continuing.

Banker is driving in the car with his mother, asking her questions, and it’s clear that the woman he’s known all his life is disappearing. Moment-by-moment changes are hard to mark, and every once in a while the family members have to stop and come to terms with what’s happening. The camera on the dashboard watches Banker and his mother as they just sit in the car, in silence, each looking out their own window. There wasn’t a word exchanged, but there is not an actor alive who could have silently rendered that feeling of loss and powerlessness so poignantly. Filmmakers like to hide behind the camera, and few have the courage to expose themselves so completely.

It was that moment that telegraphed the heart of the film, to me at least — that there’s no need to fill the moments you have left with someone with meaning, because they will fill themselves regardless of what you do. And as Banker White documents his mother’s life as it winds to a close, we see that it is filled with the quality of the relationships she’s built and the life she’s led.

We’re right there with Pam White when she says at the end of the film, “no regrets.”

The Genius of Marian premieres on PBS’s POV series next Monday night, September 8.  Check here for your local listing.