The central, shattering twist of "Incendies" is the revelation that the twins' father and their long-lost brother are the same person. Their mother, Nawal, gave birth to a son, Nihad, as a teenager after a forbidden love affair. The baby was taken from her and placed in an orphanage. Years later, during the civil war, Nawal was imprisoned and systematically raped by a torturer known as Abou Tarek. This torture resulted in the birth of the twins, Jeanne and Simon.
The twins' quest leads them to discover that their brother, Nihad, was caught in the war, became a child soldier, and was eventually trained to be the very same torturer, Abou Tarek, who assaulted their mother. Therefore, their half-brother is also their father. The moment of anagnorisis for Nawal occurs years later in a Canadian swimming pool, when she sees the three-dot tattoo she had placed on her infant son's heel on the foot of the man she recognizes as her rapist. This devastating realization causes the stroke that leads to her death. The two letters she leaves are both addressed to Nihad: one, 'for the father,' is filled with contempt for her rapist, and the other, 'for the brother,' is filled with love and forgiveness for her lost son. The film ends with the twins delivering the letters to Nihad and finally placing a headstone on their mother's grave, signifying that the promise has been kept and the truth has been faced.