Gabe & Karen & Tom & Beth: Left to right, Lisa Emery, Matthew Arkin, Julie White, and Kevin Kilner spar in Dinner With Friends.Photo: Joan Marcus

Slowly but surely, Donald Margulies is establishing himself as one of our leading playwrights. Four of his plays are of prime importance: The Loman Family Picnic, Sight Unseen, Collected Stories, and now the wonderful Dinner With Friends.

Two married couples have been best friends for years. In their Connecticut home, Karen and Gabe, international food writers, are giving a dinner for Beth and Tom, which he doesn’t attend. It emerges from the heartbroken Beth that he has left her for another woman, Nancy. Gabe and Karen are almost as crushed, having expected “to grow old and fat together, the four of us.” When Tom shows up at his home in the next scene, late at night, he is enraged that Beth broke the news of their breakup in his absence. Late as it is, he rushes over to his friends in the next scene to present his side of the story.

Act Two begins with another dinner, twelve and a half years earlier, in a summer house on Martha’s Vineyard, where Karen and Gabe are introducing Beth to Tom. Then we skip to five months after the events of Act One, as Beth reveals to Karen, on the summer-house patio, that she has fallen in love with an old friend whom she intends to marry. Rather than share in Beth’s happiness, a shocked – and envious – Karen does everything to dissuade Beth, who justifiably resents her meddling. Later that day, in a Manhattan bar, Tom, a lawyer, tells Gabe about his happiness with Nancy, to which Gabe reacts sourly.

Still later that night, Gabe and Karen are going to bed in the Vineyard house, and discuss the Tom-and-Beth situation, as well as their own by-now-uneventful marriage, in which they soldier on without much passion and with some misgivings, clinging to it like the shipwrecked to their raft.

From this already you can gather that there is skillful construction here, as well as keen psychological insight. Thus Tom and Beth end their aforementioned angry confrontation by hungrily enacting the beast with two backs. Thus Tom’s racing over to his friends to justify himself has an additional motive: Karen’s fabulous lemon-almond polenta cake that Beth tells him was a comfort to her and whose leftovers he’s dying to taste. Thus the strength and weakness of a stagnant marriage are emblematized in the ritual of folding a bedspread in perfect harmony but with robotic emotional detachment.

Margulies is a master of observing what might seem old hat with fresh eyes, hearing it with fresh ears. When the jealousy-racked Karen wonders about Beth’s long-standing infidelity, “We saw them practically every weekend in those days; when would she have had time for an affair?” Gabe answers, “I don’t know, during the week?” This is funny, especially as Matthew Arkin delivers it, but with an underscoring of wistfulness. Throughout, this ostensibly contented pair give off an aroma of envy as their opposite numbers cut loose from the time “when practical matters begin to outweigh abandon.”

Take Beth’s confession that during some stupid action movie she refused to fondle Tom’s crotch:

Karen: “Was this before or after the girlfriend?”

Beth: “Must’ve been after.”

Karen: “That’s right, one more nail in the old coffin.”

Beth: “You got it.”

Gabe: “See that? One lousy hand job, you could’ve saved your marriage.”

Karen: “Gabe!”

You can feel that Karen’s exclamation is only partly concern for Beth’s feelings.

Daniel Sullivan’s inventive direction helps immeasurably, as does Neil Patel’s perfect-pitch set design. Matthew Arkin superbly lets Gabe’s doubts peek through his certainties; Lisa Emery does Karen’s edginess on the threshold of hysteria splendidly. As Beth, Julie White again proves herself a complete comedienne down to those little inchoate noises that convey seismic tremors; as Tom, Kevin Kilner goes from likable to ludicrous without skipping a beat. Dinner With Friends is entertainment as succulent as it is sobering.