Protagonist (2007)

GOING TO EXTREMES Hans Klein stars in this intriguing look at the strange lives of four fanatics

A former German terrorist once in cahoots with Carlos the Jackal, a gay Christian evangelical who, during his avowedly ''ex-gay'' period, preaches that Jesus has cured his ''homosexual problem,'' a bank robber, and a martial-arts devotee don't walk into a bar in Protagonist. They do, however, form the four male pillars of Jessica Yu's intricate, novel, and altogether fascinating art-piece documentary. The filmmaker incorporates ancient components of drama — including the universal appeal of puppetry — to explore the shaping of character in the crucible of fanaticism. And she relates her subjects' odysseys to principles of Greek tragedy, pausing to explain such concepts as ''provocation'' and ''catharsis.'' (Those puppets? They form a Greek chorus.)

If all this sounds awfully classroom-bound, it isn't — far from it. Each man's story as he tells it is riveting, truly stranger than fiction, and awesome, too, in the way of unfathomable humans. And Yu (who made In the Realms of the Unreal, about ''outsider'' artist Henry Darger) fits her inventive artistic choices to a rigorous, well-thought-out thesis about the tragedy of the extremist — and what makes a man a man. B+