Michael Weston and Aya Cash in South Coast Repertory's 2014 world premiere production of "Trudy and Max in Love" by Zoe Kazan. (Debora Robinson / January 8, 2014)

Billy Crystal probably said it best in "When Harry Met Sally...": "Men and women can't be friends because the sex part always gets in the way."

Trudy and Max certainly try to be friends, and they maintain that platonic bond right up until the, ah, climax of the first act of Zoe Kazan's new play "Trudy and Max in Love," now in its world premiere at South Coast Repertory.

From then on, the relationship encounters problems, not the least of which being the fact that Trudy is happily married and has been for six years. However, her hubby is out of town a lot, so when she strikes up a close friendship with a fellow writer, well, what would you expect?

Kazan (the granddaughter of famed director Elia Kazan) is an accomplished movie actress ("Ruby Sparks") who shows tremendous skill as a playwright, worming her way through and around the maelstrom of human emotions. She may take her own sweet time to accomplish this task, but literary conservatism should come eventually.

Her title characters thrust and parry their emotions as Trudy attempts to balance her genuine love for her husband (who's never seen onstage) and her new lover, who shares her passion for literary creativity. It's a tightrope-walking adventure that, in most instances, works quite well under the sensitive direction of Lila Neugebauer.

What hinders the play's progress, though only moderately, are scenes — mostly involving the two supernumeraries in the cast — that veer from the situation at hand, as well as the extended moments of silently strained tension between the two main characters. With some judicious pruning, Kazan would have a gem with a fine cutting edge on her hands.

Most impressive in the SCR production is Aya Cash's splendid performance as Trudy, who wrestles with her conscience before choosing to follow her heart into uncharted waters. Cash is Kazan's onstage voice in the dramatic comedy, and her fits of hesitation, followed by bursts of romantic zeal, are both effective and credible.

Michael Weston as Max, 11 years her senior (though he doesn't appear so, hence a light beard to age him?), plays a curious character, a nice-looking chap who managed to maintain his virginity through high school and college. Now approaching 40, he's still unwed, though he dates models and exudes masculinity.

Together, they're a perfect — albeit uncomfortable — fit. Their slowly building friendship in the first act is skillfully presented, while their fervent passion in the second intensifies their characters and opens new chasms of emotional peril. Loving one person, at least for Trudy, is difficult enough; loving two on an equal basis may be impossible.

Stirring the situation even further are two characters Kazan has dubbed the Other Woman and the Other Man. Celeste Den and Tate Ellington provide strong emotional support for the main characters in a variety of assignments, both receiving ample opportunity to display their talents, often in scene-swiping style.

Their inclusion represents both a plus and a minus for Kazan's story. While both actors generate fully formed character cameos, their presence often detracts from the thrust of the play, presenting interesting yet superfluous moments — or, more technically, rest periods for one of the principal performers.

The bland unit setting by Laura Jellinek is a stark white area that functions as the backdrop for the writers' room, Max's apartment and various eating establishments. Melanie Watnick's modern costumes serve the action well, while Lap Chi Chu's harsh lighting effects help to stir emotional discord.

"Trudy and Max in Love" offers a strong conjoining of romance and reality in a tale of two people whose emotions are laid bare, as is their vulnerability. It's a promising effort from the granddaughter of one of Hollywood's finest directors in its compelling world premiere at South Coast Repertory.

TOM TITUS reviews local theater for the Daily Pilot.

If You Go

What: "Trudy and Max in Love"

Where: South Coast Repertory, Julianne Argyros Stage, 655 Town Center Drive, Costa Mesa

When: 7:45 p.m. Tuesday through Friday; 2 and 7:45 p.m. Saturday; 2 p.m. Sunday

Cost: Start at $22

Information: (714) 708-5555 or http://www.scr.org