As Franck, the sporty, shifty boyfriend of Emilie Dequenne's directionless young graduate, Duvauchelle is by turn coldly and charmingly cavalier — the only sinuous character in an otherwise airless dramatic setup.
As Florence — assistant, dog walker and minder to Roger's affluent brother's family — Gerwig is that impossible mix of gorgeous and totally real: she oxygenates an otherwise airless story.