Slowly, we were sinking into the muck.

On that raw November morning in Ukraine, a sharp wind slicing into our faces, we weren't sure we would be able to start filming, let alone finish.

But we had to. For we had brought with us a silver-haired Ukrainian woman, Olga Chernobaj, who witnessed what happened here more than 60 years earlier. She was possibly the last person alive to have observed the machine-gun execution of thousands of Jews, in the summer of 1941.

My mother, Sonia Reich, was supposed to have been one of them. But somehow, at age 10, she had escaped, and now we were telling her story on film - or trying to.

As the cameras rolled, and as the old woman tried to describe the unfathomable scene, the mud seemed to be giving way underneath us. Slowly, inch by inch, we were slipping into earth that had devoured so many souls. All the while, the old woman wept, reliving experiences she never has been able to forget.

At this moment - as a frigid Ukrainian winter hovered in 2004 - I understood fully, for the first time, why we were making "Prisoner of Her Past," a documentary that opens today at Chicago's Siskel Film Center. Why a crew from Chicago-based Kartemquin Films had traveled halfway around the world to capture such sorrow.

For we weren't merely revisiting my 2003 Chicago Tribune article, which described my mother's stunning, late-in-life belief that her Holocaust experiences were happening all over again.

By making "Prisoner of Her Past," we were putting flesh and blood on the ghosts that haunt my mother - and countless other survivors of childhood trauma. If we could show on film the terrors my mother experienced as a child, then demonstrate how an otherwise alert woman believes (to this day) that she is soon to be executed, we would illuminate a virtually unknown mental illness: late onset post-traumatic stress disorder.

We could show the doctors who originally misdiagnosed my mother that just because you're old doesn't mean you have Alzheimer's or any other form of dementia. And we would establish, once and for all, that childhood trauma, left untreated, never goes away and, as in my mother's case, can unravel a life.

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Filming my mother never was going to be easy. Less than 5 feet tall but ferocious to the core, she routinely threw doctors and orderlies out of her room in a suburban nursing home. If they got too close, she heroically took swings at them.

Believing that her life was in constant danger, she slept every night for years in the nursing home sitting in a chair, fully clothed, her bag always packed in case she suddenly had to flee. This was an echo, no doubt, of the years she spent running and hiding during World War II near the massacred village of Dubno, in easternmost Poland (borders were redrawn after the war, placing Dubno in Ukraine).

So in 2005, when I arrived at the nursing home with a Kartemquin film crew, I feared that the filmmakers' camera equipment might not survive the presumed confrontation with my mother.

Not to worry. As soon as director Gordon Quinn and producer Joanna Rudnick plugged in their gear, my mother launched into her performance.

"Welcome to my palace," she said directly to the camera, dripping with sarcasm, as she surveyed her drab-looking room.

"How do you like my beautiful view?" she asked, gesturing to the dismal parking lot outside her window.

Could this woman, so mentally acute, so lacerating in her comments, also be so profoundly delusional?

I sadly knew the answer, and my mother often confirmed it.

Frequently she insisted that someone was 'trying to put a bullet in my head,' and that yellow Stars of David had been sewn onto her clothes. Two realities were unfolding in my mother's psyche - the past and the present - and they were plain for the camera to observe.

After the arduous shoots in Poland and Ukraine and all the sessions filming my mother at her nursing home, I thought we were done with our location work.

I was wrong.

While covering the cultural devastation in post-Katrina New Orleans, I discovered practically an entire city in the grip of post-traumatic stress disorder. It was as if the story I had been trying to document in Eastern Europe had followed me back home to America, where the children of New Orleans were trying to cope with traumas of their own.

When I told director Quinn about the psychiatrists I encountered who were trying to help these kids, Quinn said he was coming to meet me and bringing a crew. In short order, we were filming the girls of Xavier Prep School as they described their post-Katrina horrors: running from the rising floodwaters of the Mississippi River; being attacked in the Superdome; losing touch with their family and friends; learning about those who died before they could say goodbye.

I was shocked - though I shouldn't have been - to discover that some of these girls were starting to act just as my mother was: terrified, paranoid, delusional.

But the kids were receiving the kind of psychiatric interventions that my mother, and most of the rest of her generation, never did. Because these teenagers were brave enough to tell their stories before Quinn's camera - even as their tears flowed - they will educate the world about the consequences of childhood trauma.

They, like my mother, are the heroes of this film.

Reich may be contacted at hreich@tribune.com