This low-key sex farce may be a minor effort for director Jan Hrebejk (Up and Down, Beauty in Trouble), but it still advances his generous worldview. As usual he fashions a knowing portrait of the Czech bourgeoisie that’s neither complacent nor mean-spirited, and the characters seem real enough that you can imagine them existing outside the plot. The movie depicts two long-married suburban couples, all of them close friends, who decide to experiment with group sex; to everyone’s surprise, it works out just fine. Sincerely and affably, Hrebejk asserts that normal life doesn’t have to be dull and that sex is good for you. The original Czech title translates as “The Holy Quaternity.” In Czech with subtitles.