"The Pillowman" is a fiendishly clever, somber but briskly comic play about many things. But as staged by Pittsburgh Irish & Classical Theatre to open its 10th season, it is above all an engrossing moral crack-the-whip for the audience, who have to keep readjusting their sympathies as playwright Martin McDonagh springs one surprise after another.

Suellen Fitzsimmons From top, Tom Atkins and Simon Bradbury play policemen interrogating Alex Moggridge in "The Pillowman." Click photo for larger image. 'The Pillowman' Where: Pittsburgh Irish & Classical at Henry Heymann Theatre, Stephen Foster Memorial, Oakland. When: Through May 28; Wed.-Fri. 8 p.m., Sat. 2 and 8 p.m.; Sun. 2 p.m.; no matinee May 13. Tickets: $26-$36; students $15; 412-394-3353 or www.picttheatre.org.

A scary interrogation drama to start, complete with a good cop-bad cop duo (one humorous, one sadistic), it quickly turns into a detective puzzler, as characters and audience try to make sense of three recent child murders. Then the issue becomes survival, human and artistic, and audience members who don't keep reassessing their moral stance aren't really paying attention.

The prisoner, Katurian, is a writer who lives in an (unnamed) oppressive dictatorship. Because of that and the content of his brief, dark parables, he is almost entirely unpublished. He is also talented, with a great gift for macabre invention. But when you get past the lurid details of his stories, which have to do with perversely abused children, you look out on a sea of sadness, devoid of human warmth.

And yet the story that gives the play its title pulsates with empathy for the human condition. I think of James Agee's lines: "Now, on the winsome crumbling shelves of the horror, God show, God blind these children!"

All this torment directs our attention to Katurian's past, which he reveals in a longer story, "The Writer and the Writer's Brother," which he calls "the only story of mine that isn't really fiction."

Katurian does have a brother, slightly older and mentally challenged, though just how challenged isn't clear. The two were also abused, we learn, and by parents who, in a perverse parody of Katurian's own attitude, value art and posterity over humanity.

Katurian is an articulate defender of the autonomy of the artist and his art. But as we follow the dark windings of his personal story, we have to waver in our sympathy. We get insights into the cops, too, bringing further complication. In their pursuit of something they can call truth, they are like us; perhaps we share their disgust. Surely we question Katurian's hard-line insistence that the first (or only) duty of the artist is art.

"The Pillowman" inhabits a Kafka-esque world of shifting truths, over which McDonagh rules like a comic, post-modern Father Grimm.

But don't take the children to see it, because Katurian's stories are really bizarre, no matter how comically inflated in the telling.

The central conflict is between the bewildered writer, played with appealing immediacy and transparent pain by Alex Moggridge, and the two cops. Tom Atkins, in his PICT debut, is the "good" cop, Tupolski, and Canadian actor Simon Bradbury plays the ironically named Ariel, the sadist. Of course we have to readjust those labels, too.

Atkins and Bradbury are a perfectly complementary pair, the former large, genial and weathered, very official in a suit but happy to shatter the air of institutional menace with a joke, which makes his own flashes of violence the more shocking. Atkins is especially at home with the dry, wry comedy, and his telling of Tupolski's cosmic parable is a lesson in comic timing.

Bradbury is the seething street tough of the two, and his slight stature makes his menace all the more frightening. He plays off Atkins with skill: You'd think these guys had been on stage together before. But none of their fireworks would ignite without the resisting force of Moggridge, who has steely resolve beneath his friendly, even ingratiating face. His brother, Michal, is played by Matt Gaydos as an enigmatic mix of big baby and shrewd manipulator.

Stuart Carden, who we've seen direct mainly comedies, shows a firm hand with the mixed genres here. If anything, there are times when the tension might be ratcheted up a bit, and the long scene between the two brothers goes a bit slack because of the length. But none of this lessens the play's impact. Anne Mundell adds a blandly institutional set that contains secrets of its own.

"The Pillowman" deals with disturbing material, challenging one's trust in art, but its very theatricality goes pretty far toward reaffirming that trust. I think.