François Grimbert (played as a young boy by Valentin Vigourt and as an adult by Mathieu Amalric) grows up in Paris in the 1950s.

He is the skinny, sickly son of two marvelously athletic parents, Tania (Cécile de France) and Maxime (Patrick Bruel).

Only gradually does he learn of his parents' tragic past and that he had a sibling — a half-brother named Simon, his father's first son.

François knows that his parents met sometime around the war, and he imagines their courtship and marriage in the shadow of atrocities which nobody talks about any more.

The site's consensus reads: A "Secret is poignant, sad, and beautifully crafted, featuring fine performances that stave off a drift toward soap opera territory".