Starring Mathieu Amalric and Cécile de France. In French with English subtitles. Rated PG. Opens Friday, August 1, at the Park Theatre

This isn’t the first time Claude Miller has made a film about a troubled child with imaginary friends. The unhappy hero of his 1998 feature La Classe de neige habitually escapes into a dark fantasy realm to obscure the fact that his father is a serial killer. Conversely, Franí§ois’s dream-time brother, Simon, did exist in the (muscular) flesh, only never while Franí§ois himself was drawing breath. How this came to be is the subject of Un secret, a Holocaust drama in which jealousy and desire turn out to be as potentially hazardous as Adolf Hitler, political collaboration, and Pierre Laval.

Beginning in 1955, the story travels backward in time to 1936 and forward to 1985. The adult Franí§ois (Mathieu Amalric, his childhood predecessors being portrayed by Valentin Vigourt and Quentin Dubuis) works with autistic teenagers, young people even more alienated from the world than he himself is. He discovers that the idyllic marriage he once believed his athletic parents, Tania (Cécile de France, a thesp who is now as much of an on-screen Gallic presence as Gerard Depardieu was a quarter of a century ago) and Maxime (Patrick Bruel), had is much more problematic than he ever imagined. How he gradually comes to terms with a tragedy in which everyone is a victim and no one a villain forms the essence of the plot.

Despite the off-screen horrors, Un secret unspools almost like a holiday film. More than half of the scenes take place at the beach, in the woods, in the gym, and—especially—at a swimming pool that looks as if it were specially constructed for the 1936 Berlin Olympics.

Thus, when Tania falls backward off the 10-metre board, all Europe falls with her. And when she swims happily underwater, we realize that all the chlorine in the world won’t wash away the pollution into which she was so unwillingly dipped.