Sarah Polley’s vibrant, funny and honest portrayal of family as it really is also turns out to be a bold new way of storytelling that explores the creative process itself.

As the movie ended, I cried. Not a little—these were torrential, impolite, and irrational tears, the likes of which had not touched my face since my father died over a decade ago.

It made little sense. The film I had just seen was Stories We Tell, a 2012 documentary about secrets that swirl around the Polleys, a showfamily from Toronto, and was put together by youngest of that clan, the ethereal indie actress and Oscar-nominated filmmaker Sarah Polley. It had ended on a light, even comical note of discovery. But none of that mattered: this film about how we craft identity out of the stories we tell about ourselves and our family had left me a wasted puddle of emotions. Employing the same Socratic method that the film does, it was my job to figure out why.

• Is it because it is a film about loss? It’s true that the central figure of Stories We Tell is missing: Diane or Mum (which one she is depends on who is telling the story) died the week the filmmaker turned 11, leaving a towering shadow to the people who knew her. Hearing her described by her children and husband, her friends and lovers, the figure that emerges is not simply the life of the party but the Godzilla of it, with her mild-mannered husband cowering in her wake.

Diane was a lover of life—and quite few men that one summer in Montreal, it turns out. Indeed, the first third of the film is a kind of whodunit, with the central mystery the identity of Sarah’s biological father. Was it Geoff, the charming actor? Harry, the film producer and stage-door Johnny? Or Michael, Diane’s husband and the man who raised Sarah believing he was her biological dad? This film is more an experiment in storytelling than a traditional documentary so Polley isn’t limited in her means to tell the story she wants to tell.

• Is it because it’s a film about family? The Polleys are a sardonic, sarcastic and tender bunch—the types of brothers and sisters who poke a bruise until you cry and then hug you through your tears. Sarah first started thinking about the question of her paternity because her four older siblings were making fun of how different she looked from her dad. “This is really a lesson about using birth control when you’re having an affair,” is one brother’s take on the story. “Thanks a lot,” says Sarah. This is a vibrant, funny and honest portrayal of family as it really is, and not how we hope or pretend it to be.

• Is it because it’s about the creative process? Let’s face it, most of us have tried to transform our turbulent family histories into art at some point in our lives, and the process tends to drive us a little crazy. Polley is no different: the more she pries and investigates, the more the very subject of her film eludes her. Is it about the nature of identity or storytelling? It is thrilling to watch the brave (but far from fearless) way she wrestles with these questions—whether trading barbs with her siblings or coaxing raw emotions from her father as he records narration or handles her interrogation. When her dad calls her a “sadistic director” it is not only a heartfelt compliment, but in some ways also one of the kindest things ever said of a female filmmaker.

Honestly, it could have been all or none of those things that got me in the end. This film is an intricately layered onion, and you know what happens when you cut one open. It is fitting, though, that my answer should remain out of reach: this is a movie that shows us that any answer to a question is itself another question, and that the stories we tell are as much a mixture of the joy and longing that animate our spirit as they are truthful recollections of the past. “A story isn’t a story when you are in the middle of it,” says the man who raised her. “It is just a confusion.” True, and rarely has confusion ever been more beautiful, more essential, than it is in Stories We Tell.