CARNAGE “This water-skiing squuirrel video is a lot less amusing than Mark’s email led us to believe.”

ONE SUNNY DAY on a Brooklyn playground, a kid hits another kid in the face with a stick. Is it a vicious assault, or a perfectly normal childhood brawl? The line between "kids being kids" and "kids being reprehensible little monsters" provides the ostensible source of conflict in Roman Polanski's dark new ensemble comedy Carnage, but the real issues at stake go much deeper: What happens when agreed-upon social boundaries are transgressed? How about when we realize we never agreed on any boundaries in the first place?

The entirety of Carnage is set in an apartment where four parents have gathered to discuss how the playground stick/face incident will be resolved. Alan (Christoph Waltz) and Nancy (Kate Winslet), parents of the stick wielder, are happy to punish their kid and be done with it, but Penelope (Jodie Foster), mother of the wounded, requires more than an apology: She wants to make sure Alan and Nancy admit just how reprehensibly their son has behaved. And, being a perfectly composed bobo housewife with a flair for flower arrangements and an interest in African genocide, she's going to extract her pound of flesh in the smuggest and most condescending way possible, whether her husband (John C. Reilly) likes it or not.

The conversation between these four begins politely enough, and ends with drunkenness, shouting, vomit, and accusations of hamstercide. None of these characters come out unscathed, and determining which among them is the most despicable is something of an audience Rorschach test. (The acting is impressive across the board, but fans of Reilly in particular should take note.) But this tale of rich people behaving badly is rooted in real truths about human behavior: how parental protectiveness can turn blind and ugly; how social niceties often mask complete indifference. Fortunately, the script—by playwright Yasmina Reza—is penetratingly funny, and watching these truths play out is never less than thoroughly entertaining.