What Jean-Claude Van Italie's "Mystery Play" most definitely is not is a mystery play -- although an impassive butler circulates regularly among the cocktail party guests on stage, the lights keep going out and one corpse after another crashes to the floor.

Van Italie was a hero of the experimental theater in the 1960s, the man who excoriated the violence and mindlessness of the national temperament in "America Hurrah." "Mystery Play" had an infinitesimal run off-Broadway in 1973 and has now been revived -- with a certain reckless courage -- by the Woolly Mammoth Theatre Company.

It is a quirky, opaque piece -- Agatha Christie turned inside out and larded with metaphysical clues and just as many metaphysical red herrings. Role-playing is apparently one of its prime concerns, but it could be about predestination. Or seeming versus being. Take your pick. Or cook up your own interpretation.

A bloodhound before the fact, the mystery writer presides over the party, giving detailed instructions about the crimes to come, counseling each guest on his movements, motivations and reactions. ("You seem a lunatic and may have every good reason to appear one," he advises one. To another: "You play the role of the butler -- very badly.") Then having set up the scenario, he shouts "Ready, go!"

The various characters -- a senator, his wife, his son (a schizophrenic, hence played by two actors), a college professor, a starlet and the butler -- dutifully follow the writer's commands, until they meet their demise. But death does not silence them. They all get back up and deliver post-mortem monologues. The professor rhapsodizes over Alexander the Great ("If he was born at all, he was born of woman . . . like myself.") The starlet does an anatomical come-on. ("Would you like to examine my vital organs?") The senator indulges in some right-wing hysteria and his wife confesses that "to be alone without etiquette is terrifying to imagine."

Some of this is mildly intriguing; much of it is rather willful claptrap. What is notable is not so much the material, but the conviction Woolly Mammoth manages to bring to it. If you can divorce yourself from Van Italie's vagaries, this is one of the company's better-staged productions. The acting, although not yet uniformly good, is gaining in assurance. Richard Bertone (the mystery writer), Carroll Carlson (the senator) and Kirsten Vance (the starlet) offer distinctly etched performances that encourage you not to give up totally on the script. The set and costumes are tidy as a pin, and director Roger M. Brady has imposed a crisp, brittle style on the proceedings.

While I don't imagine "Mystery Play" will win Woolly Mammoth many new converts -- it is the sort of play that leaves general audiences bewildered -- it further defines that company as one in vigorous pursuit of a singular identity. A willingness to take on eccentric and marginal plays is Woolly Mammoth's strength in the local hierarchy of theaters. "Mystery Play" represents the risks such an approach entails. But the willingness is still commendable.

MYSTERY PLAY. By Jean-Claude Van Italie. Directed by Roger M. Brady. With Richard Bertone, Carroll Carlson, Robin Phillips, Jerry Clarke, Gwendolyn Briley-Strand, Kirsten Vance, Paul DeSandro, John Mulligan. At the Church of the Ephiphany through Nov. 20.