They meet cute: Isabelle (Eva Green) is seemingly chained to the door of the Cinematheque Francaise in Paris in 1968 when she begins chatting up Matthew (Michael Pitt), a naive young American student. She's protesting the firing of Henri Langlois, the institution's founder. Matthew is lost without an old movie to light his lonesome days.
Not to worry, Matthew. Isabelle and her saturnine brother Theo (Louis Garrel) have a sort of home movie--no camera but lots of sex and nakedness--that they think might be fun to make in their parents' apartment. After the clueless mother and father depart on vacation,...