The Oscar-nominated French Canadian drama “Incendies” takes us from Montreal to Lebanon as two 30ish siblings try to unravel the mystery of their mother’s life and flight from that country decades before.

Not that it identifies those locales right away. One of the maddening things about Denis Villeneuve’s film of Wajdi Mouawad’s melodramatic play is the stingy way it doles out simple geographic information like that. And when you’re building your story in geographic episodes, that’s too basic to skip over.

Jeanne (Mélissa Désormeaux-Poulin) and Simon (Maxim Gaudette) have differing reactions to their mother’s last request, a plea contained in her will. “Find your father,” she wrote. “Find your other brother.” They didn’t know they had either. Jeanne is guilt-ridden enough to take a shot at that quest. Simon is too angry to even try.

As Jeanne returns to Lebanon to retrace her mother’s steps, flashbacks begin to tell the story of mom, Narwal (Lubna Azabal), of forbidden love between Christian and Palestinian, the horrors of Lebanon’s Christian/Muslim (Palestinian) civil war. Massacres, rape and torture turn up as the various clans clash and Jeanne experiences a hint of the hostility that made her mother flee.

As the tale turns darker and Jeanne interviews more and more people who knew or knew of her mother, her journey takes her to prison and into the dark recesses of mom’s past. Jeanne’s own memories of her mother start to connect to her mother’s story, giving her further clues. Eventually, Simon must join her to complete the quest.

The performances — especially Azabal in the flashbacks — are engrossing as is the story the actors are telling. The film’s moving flashbacks are contrasted with the sometimes over-the-top revelations that brother and sister discover in the present day. The “big reveal” here is bit obvious, no matter how “out there” it aims to be.

Thus, “Incendies” is occasionally compelling, but also overlong and vexing in the ways it draws out a “shocking” conclusion that we unravel long before the characters do.

MPAA rating: R for some strong violence and language.

Cast: Lubna Azabal (Narwal), Mélissa Désormeaux-Poulin (Jeanne), Maxim Gaudette (Simon).

Credits: Written and directed by Denis Villeneuve, based on a play by Wajdi Mouawad, produced byLuc Dery and Kim McCraw. A Sony Pictures Classics release. Running time: 2:10.