What makes William Shakespeare’ s “The Merchant of Venice” a problem play is not the plot, the dialogue or the story structure. It’ s the fact that society has changed in the 400-some years since the Bard wrote it. Directors, in various attempts to make the play relevant to modern audiences, have set it in Nazi Germany and the streets of post-Sept. 11 London.

Maine’ s Theater at Monmouth chose to place it in the early 1960s when John Fitzgerald and Jackie Kennedy were in the White House — America’ s equivalent of Camelot.

In the end, however, the setting doesn’ t really matter. “The Merchant of Venice,” much like “King Lear,” rises and falls on the performance of one actor. Whoever plays Shylock, the Jewish moneylender, must walk a razor-thin line that allows an audience to sympathize with his plight and even be outraged by it but also to see his many flaws. Any actor who strays too far to either side, runs the risk of slicing the multilayered character to shreds, leaving an audience with a ragged caricature.

Bill Van Horn, an eight-season veteran of Monmouth, gave a near-perfect performance as Shylock last Friday, opening night. Van Horn is a big man with a booming voice. His size alone was intimidating on the Cumston Hall stage.

Yet, it was the way Van Horn wore Shylock’ s anger, as if it were a warm, fuzzy blanket spun with gold thread that made the character so mesmerizing. In nearly every one of his scenes, theatergoers in the same instance were intrigued and repulsed by Shylock’ s behavior. Van Horn created a man so mean, so cruel, so unable to express love even to his own daughter that when he was an outcast at the end of the play it was hard to muster sympathy for the Jew, except for the fact that the actor’ s portrayal was so utterly, so perfectly human.

Anna Soloway as Portia matched Van Horn’ s performance in excellence, yet was in many ways its opposite. The actress shed light, while the actor’ s Shylock emitted darkness.

Soloway’ s Portia also was one of the few characters that was not intimidated by Van Horn’ s Shylock. The actress delivered her “quality of mercy” speech in so matter-of-fact a manner that she sounded like a lawyer making a legal argument in a modern courtroom. She captured beautifully the young maid bound by duty, eager to love, possessing a wit and wisdom that will be admired by the men in her life but rarely treasured.

The rest of the cast proved their equals for the most part. Dustin Tucker, as Bassanio, suitor to Portia, was not quite comfortable in the character’ s skin opening night but was close to capturing his charming loyalty. Dennis A. Price as Gratiano, J. Paul Guimont as Lorenzo and Kristen Burke as Shylock’ s daughter Jessica gave standout performances.

Dan Olmstead as Antonio, the merchant who owes Shylock a pound of flesh, created a two-dimensional character — glum and glummer. The actor’ s dull portrayal made it nearly impossible for the audience to see why Antonio’ s friends would risk so much for him.

And then there was Mark S. Cartier. Another Monmouth veteran, he knew exactly where the comedy is buried in “The Merchant of Venice” and, as always, he mined it effortlessly as Launcelot Gobbo, Shylock’ s servant.

Director Jeri Pitcher failed at drawing obvious parallels to JFK’ s three short years in the White House. Yet her decision to set “The Merchant of Venice” in the 1960s worked on another level with help from costume designer Mara Famiglietti, set designer Chez Cherry and lighting designer Lynne Chase.

Pitcher tapped into the same 1960s angst and ambiance that has proved so compelling in AMC television’ s original series “Mad Men.” The gray suits, white shirts, narrow ties and fedoras made the men of Venice appear as constrained by their lifestyles as Shylock is by the laws that restrict where he may live and earn a living. In this setting, Portia seemed to be a woman several years ahead of and at odds with her time — Shakespeare’ s own Betty Friedan.

With “The Merchant of Venice,” Monmouth has succeeded in giving audiences some weighty and, perhaps, timeless, issues to ponder along with an evening of fine entertainment. This production is a shining example of how with the right Shylock balanced with an authentic Portia, Shakespeare’ s problem play need not be much trouble at all.