The last time I was inside Polish Hill's old Emma Kaufmann Clinic, about two years ago, it was because some activists had turned the now-vacant building into a makeshift free clinic for G-20 protesters.

The building has a much different feel hosting Quantum artistic director Karla Boos' adaption of the Graham Greene novel. And most of the wounds in the play, emotional rather than physical though they be, go untended.

From the first, we know (or at least sense) that the affair between the writer Bendrix and married Sarah Miles will end sadly. What's haunting about the play is not that the characters won't do what would make everyone happiest; it's that they can't.

Bendrix (played by Tony Bingham) is too impassioned -- the man who would rather die than face the moment of parting after one of the couple's assignations. What drives Sarah (Gayle Pazerski) is harder to pin down. 

"One can't love and do nothing," she tells Bendrix, explaining their affair. But she won't leave her gray, mid-level-bureaucrat husband (one of several roles expertly assayed by James FitzGerald). And it's never clear whether it's because of propriety, because she thinks it's wrong, because it would hurt him too much -- or because of God, the play's large, invisible character.

Come down to it, this anguished play's biggest conundrum is arguably the existence and function of that higher power. Both Bendrix and Sarah profess not to believe in God -- but the idea of God shadows their every move.

Sarah even uses that idea as an analogy to explain how the lovers can be apart. "People can love without seeing each other," she tells Bendrix. "People go on loving God, don't they, all their lives, without seeing him." 

The script has a certain transparency that might be mistaken for oversimplication. These characters are, throughout, as naked emotionally as they occassionally are physically. That transparency is the quality of a vitrine that simply contains a greater mystery.

The show is acted with craft and commitment (that's Bingham and Pazerski, pictured) and directed by Martin Giles on a striking set by Tony Ferrieri.

Quantum (www.quantumtheatre.com) stages The End of the Affair through Sun., Oct. 30.