Joanna and Michael Reed (Keira Knightley and Sam Worthington) are young, rich, beautiful and married in New York. But don't hate them. They're struggling with the seven-year-itch. Michael goes on a business trip to Philadelphia with colleague Laura (Eva Mendes) while in Manhattan Joanna runs into ex-flame Alex (Guillaume Canet, who is Patrick Dempsey's shaggier, Gaulish doppelganger). Will they or won't they cheat? That's where the suspense lies. Knightley and Canet are in a different class than either Mendes or Worthington, an action star (Avatar, Terminator: Salvation) whose work here misses the subtlety required by the role. Fortunately, we spend much more time in New York. Last Night suffers a little for the imbalance, but these are sexy people, offering a diverting portrait of emotional versus physical transgression. In support, Griffin Dunne's presence brings a welcome touch of Martin Scorcese's lost-in-Manhattan movie After Hours to the piece.