Truth is a tricky thing. Memories can falter, secrets are clung to, and there is more than one way to see an event, interpret its meaning. Wallace Stevens had 13 ways of looking at a blackbird. Rashomon's priest and woodcutter famously offered differing accounts of a woman's attack. Hey, even Johnny Cash wondered "What Is Truth?"

Sarah Polley's extraordinary documentary, Stories We Tell, asks that same question in particularly resonant, and relevant, ways. Here is a seemingly simple inquiry into the life, and death, of Polley's mother, Diane, a vivacious actress with a brilliant smile. Polley is an actress herself (she has been playing make-believe, professionally speaking, since kindergarten), and a director of the emotionally charged Away From Her (nominated for two Oscars, including one for Julie Christie) and Take This Waltz (with a love-stuck Michelle Williams). She was only 11 when her mother died, of cancer.

There was much Polley didn't know, much to be investigated.

And being a woman comfortable behind the camera, cognizant of the apparatus' ability to observe and record - and deceive - Polley set out to discover who her mother was, what she meant to other people, whether she was happy, whether she'd had lovers.

Rounding up a close circle of family and friends, and prodding (self-mockingly, at times) her own father, Michael, into reading a wonderfully eloquent and insightful narration, Polley begins to uncover facts about "Mum," and facts about herself, that - not to undersell things - are pretty earth-shaking.

Talking with her smart, charming, funny siblings, with her chain-smoking dad, with old theater company troupers, and with a Montreal movie producer, Harry Gulkin, who knew Diane, and offering up a trove of faded photographs, home movies, a mesmerizing CBC television audition tape (Diane singing "Ain't Misbehavin' "), and other key elements, Polley explores issues intimate and personal - and universal.

We all have parents. We all have histories. And we have mysteries, too - the mistakes, the regrets, the betrayals that have gone unspoken, but that nonetheless shaped us.

There has already been a lot written, and spoken, about Stories We Tell - a hit last year and this year at film festivals. You can go online and read all about the surprises and strategies behind Polley's film - and how, by its own design, it becomes a kind of commentary on the documentary form.

But I suggest you see Stories We Tell without reading too much about it. And put your hands over your ears if people start to discuss the movie. And then, after you see it, you'll be practically exploding with questions - and with awe.

Stories We Tell **** (out of four stars)

Directed by Sarah Polley. With Sarah Polley, Diane Polley, Michael Polley, John Buchan, Harry Gulkin, others. Distributed by Roadside Attractions.

Running time: 1 hour, 48 mins.

Parent's guide: PG-13 (profanity, adult themes)

Playing at: Ritz Five (opening at the Bryn Mawr Film Institute on June 7)EndText

Contact Steven Rea at 215-854-5629 or srea@phillynews.com, or follow on Twitter, @Steven_Rea. Read his blog, On Movies Online, at www.inquirer.com/onmovies.