It's about a pair of twins in Quebec, already young adults when their mother, a Lebanese emigre, dies. In her will, she tells them to find their father and their brother. They don't know who their father is, and they don't even know that they have a brother.
The film flashes back and forth between the past and present, as we see the mother's early life and her daughter's trip to the Lebanon to carry out the search (later joined by her twin brother). Much of the mother's youth took place during the Lebanese civil war, so the flashbacks can be very violent and the trail quite convoluted until the stunning moment of revelation.