Even when everybody knows what’s planned, you can never be sure of what will actually happen when friends get together. In Bruce Norris's new play “The Qualms,” what’s supposed to be a quiet evening of dinner, drinks and what used to be called “swinging” doesn’t go as expected. It’s a barbecue with a side of sexual dallying among four couples.

Norris’s comedy, directed by Pam MacKinnon, is running at Playwrights Horizons through July 12. New York Times theater critic Charles Isherwood lets us in on the story and the performances.