If New York-based playwright Michael John Garces had written nothing but this 1999 two-act drama, he would have contributed more to the American stage than most playwrights do over a lifetime. His taut, Spartan style masterfully blends the poetic naturalism of Chekhov, the indeterminate menace of Pinter, and the streamlined brutality of Mamet, and Garces finds in unremarkable characters souls as complex, compelling, and enigmatic as any in the greatest works of theater. Acts of Mercy focuses on five men in a family of Cuban-Americans--or, more accurately, the tattered remains of a family shredded by indiscretions and betrayals lost in the haze of selective memory. The family's misanthropic patriarch, Nestor, lies dying in bed while his sons Eladio and Jaime struggle with their decades-old hatred of the man. Following his seven characters through a single evening, Garces creates relationships so rich and subtle that by the time the play ends it seems all of human nature has been exposed. And he couldn't ask for a smarter, more nuanced staging than this one by Joanie Schultz for Flush Puppy Productions, a world premiere. Like a handful of other great young directors in town (Eric Ziegenhagen, Hallie Gordon, Sean Graney), Schultz coaxes from her actors seemingly effortless performances that have titanic effects. Her cast have dug deep into the psychologies of their characters but never compromise Garces's well-honed script. There's craft evident in nearly every moment, lending even the darkest of them in this unapologetically dark play a kind of beauty. Angel Island, 731 W. Sheridan, Chicago, 773-377-5000, ext. 7411. Through February 3: Thursdays-Saturdays, 8 PM; Sundays, 3 PM. $10.