THERE ARE NO MOTHERS in fairy tales, a genre of orphans whose winding paths, however enchanted, lead to domestic conventionality. Not so in Céline Sciamma’s elliptical and enigmatic Petite maman, about a girl who encounters a stranger she has known since birth and how their incredible attachment twists the asymmetries of motherhood into a new, beguiling shape. Running to a crisp seventy-two minutes, the film begins with eight-year-old Nelly (Joséphine Sanz) bidding au revoir to the elderly residents of a nursing home one by one before arriving at the room of her maternal grandmother, who recently