Every family has its sustaining myths, although those that Sarah Polley grew up with were shakier than many. The need to resolve the stickier bits—especially regarding her previously unsure paternity—drove her to make Stories We Tell, a dazzling documentary full of unexpected twists and turns.

It took the former child actor (with more than 20 credits before Road to Avonlea) and recent director (Away From Her, Take This Waltz) five years to make the film, which opens here Friday (October 19). The process included interviewing family members and friends, collecting archival material, and, eventually, filming new material to match home movies from the 1970s. Much of this features Vancouver actor Rebecca Jenkins, who bears a striking resemblance to Polley’s mother, Diane, an excitingly erratic personality who died of cancer in 1990.

“Rebecca is an astonishing actress,” the director declares on the phone from her Toronto home. “She does such an amazing job that a lot of people don’t realize, until the very end of the film, that those scenes are re-creations. It’s a strange thing when an actor is so good you want to hide the fact that she’s in your movie. I definitely wanted people to wonder which parts were real, so it becomes something I avoid talking about. Sorry, Rebecca!”

Aside from the most personal angles, the film works as a meditation on the process of storytelling itself. Polley, 33, cultivated a necessary detachment from the emotional content, already amplified by her clan’s admitted tendency to dramatize events—in her case, literally.

Some viewers may even come away from her movie feeling they’ve heard every perspective but the director’s. “I certainly didn’t want to simply make a documentary about my family’s secrets,” says Polley, who will next be seen acting in a Wim Wenders film. “But I was fascinated by the idea that all of us were embarking on this storytelling adventure together. At times, we were helping each other, and at other times [we] were in opposition to each other. But as the person making the film, I knew I had the last word, so also having a seriously confessional voice-over seemed like it would be, you know, a little too much.”

Especially compelling is the way all participants wrestle for control of the narrative. The winner of this contest is the father she grew up with, former actor Michael Polley, whose wonderfully written essay about the family saga helps structure the story. Resolving their mysteries—and reconciling everyone’s needs in the process—has, she says, probably altered her director’s attitude toward her craft.

“I was exploring the themes of infidelity and long-term relationships in both my previous features and all of my short films. And now that I’ve made a movie about where that interest came from, subconsciously, I wonder if I now have to make fundamentally different films. Having thrown the form up in the air to see where it landed—playing with structure in very different ways than I had before—it’s going to be hard to make a straightforward film again.”

Guess we’ll just have to wait and see how her next stories are told.

Watch the trailer for Stories We Tell.