MEASURE FOR MEASURE by William Shakespeare; directed by Roger Hendricks Simon; music and songs by William Penn; set design by Ursula Belden; costume design by Bary Allen Odom; lighting design by Hugh Lester.

With Justin Deas, David Little, Moultrie Patten, Donald Warfield, Floyd King, David Cromwell, John Neville-Andrews, Jim Beard, Brenda Curtis, Marion Lines and Janice Fuller.

At the Folger Theatre through Nov. 23.

It has long been rumored that "Measure for Measure" deserved something better than its obscure nook in the Shakespeare canon, and last night, at the Folger Theatre, the rumor was handsomely vindicated.

What makes "Measure for Measure" fascinating -- even as it wanders off in as many directions as a Massachusetts Avenue traffic circle -- is the way in which the soul-searching of its main characters is tied to the overriding question of justice versus mercy. What makes this production fascinating is the way in which an abundance of good actors with meaty roles manage, under Roger Hendricks Simon's direction, to work within a single, stunning visual concept.

Bary Allen Odom's soft, colorful costumes and Ursula Belden's hard, dark setting -- dominated by black iron gates and fences -- seem almost like an inanimate embodiment of the theme: the contest between, on the one hand, understanding and human frailty, and on the other, discipline and government. (And the elaborate use of ironwork may prove to be a precedent; not only does it look very grand on the Folger stage, but Capitol Hill is a neighborhood where local craftsmen know about iron bars and fences.)

The story is set in a Shakespearean Vienna, where the ruling duke, Vincentio, decides he has become too soft a touch, judicially speaking. So he announces a vacation and names his deputy, Angelo, to run the city in his place, hoping Angelo will crack down on the various bad elements who have been running amok. And among the first of these elements is one Claudio, whose crime is to have impregnated the woman he loves, slightly in advance of their marriage -- fornication, in other words. Angelo promptly sentences Claudio to death.

Then Claudio's sister Isabella, fetched from the cloister where she has been studying to be a nun, arrives to plead for Claudio's life. His friend Lucio has asked her to use her feminine wiles with Lord Angelo, but Isabella doesn't know how to be coy. She can only make an eloquent and passionate appeal for mercy. "Go to your bosom," she entreats Angelo, "knock there, and ask your heart what it doth know that's like my brother's fault."

This modest, straightforward approach, ironically, makes her all the more alluring to him. His initial response is unyielding -- "it is the law, not I, condemns your brother," he insists -- but soon he is hinting at his corruptibility as broadly as any congressman ever videotaped by Abscam.

Isabella turns him down -- unambiguously. "More than our brother is our chastity," she says at one point. And visiting Claudio on death row, she tries to reassure him of her devotion by noting, "Were it but my life, I'd throw it down for your deliverance as frankly as a pin."

These are the play's most compelling scenes, and since the good-hearted Duke has remained in the neighborhood all the while and kept abreast of all that has transpired, there is never much suspense about the ultimate outcome. But even the later, more ramshackle course of the play -- and all the game-playing and word-playing that attend its resolution -- are absorbing stuff here, thanks to fine performances by the likes of John Neville-Andrews, Floyd King and Jim Beard as familiar Shakespearean ne'er-do-wells.

The central, and outstanding, performance is that of Brenda Curtis as Isabella, whose struggle with Angelo and her conscience is consistently absorbing and well-drawn. As Angelo, David Little is forceful and intelligent, although he hasn't yet made his surrender to temptation sufficiently vivid, or, more generally, sunk his teeth into the part. And the only problem with Justin Deas as the Duke is a tendency to let his voice run out of control at times, like a dog pulling a novice master. But he has a commanding voice, so the flaw is understandable, and it is, in any case, nothing that a little more direction couldn't cure.