The hook of this R-rated horror film would also work for a superior young-adult novel. A decade from now, the U.S. has mostly solved its crime and unemployment problems with one Hunger Games-style tweak: On one night in March it's perfectly legal for Americans to kill anyone they want to. With the wealthy locked down in their homes, it's the poor who tend to die on purge night, often at the hands of gangs of "hunters" shouting things like "Die, homeless pig!" The movie disapproves of this behavior but lends it ugly credence in the implication that the economy is booming thanks to the elimination of what Paul Ryan would call "the takers." As always in YA, one sensitive kid figures out that all of society is evil or phonies or whatever. In this case it's the excellent Max Burkholder, playing a likable inventor geek holed up with his family to wait out purge night. After some misadventures, he sees a black homeless man (Edwin Hodge) running down the street of their ritzy subdivision. The man screams "Help me!" Gunshots crack in the night. The kid, not up on his Ayn Rand, disables the elaborate security system and invites the man inside. Think Guess Who's Coming to Be a Moral Quandary? Soon, a lynch mob demands the man be surrendered-- or the family be killed. Writer-director James DeMonaco wrings this for some memorably tense scenes, but all this big-idea drama soon gives way to too many scenes of Ethan Hawke dispatching more faceless adversaries than is justifiable in a film committed to reminding us of the horribleness of violence.