François Cluzet plays “Beck,” a pediatrician who is preparing for a late-night swim with his wife “Margot” (Marie-Josée Croze) when he hears her scream and then is struck on the head, falling into the water. The story jumps forward eight years to reveal that Margot was murdered and someone else has been found guilty of the crime. Each year, Beck visits his former in-laws for the anniversary of her death, but this tim…