The arc of a relationship is never smooth or predictable. Lust—thrilling as it may be—evolves into complacency, which can become resentment as the partners battle estrangement and indifference. In this L.A. premiere of David Schulner's captivatingly constructed depiction of just such a progression, director Robin Larsen displays an impeccable penchant for clarity.

We first meet Charlie, a young Jewish man newly relocated to Los Angeles, and Hope, an Asian woman, as they return to his cramped studio apartment following a first "date." Schulner's playwriting strength is his freewheeling conversational tone and perfectly pared utterances. In the hands of actors Steven Klein and Suzy Nakamura, the dialogue jumps from the page. It's refreshingly rare to see actors who, in the short span of a rehearsal process, achieve such an interpersonal rapport that we, the audience, are completely drawn into their reality.

Great leaps in time must take place for 60 years to pass during the show's 90-minute running time. Larsen and her acting duo achieve this Herculean task with unhurried choices and some of the best technical wizardry I've ever seen in a venue this intimate. Scenic Designer Craig Siebels' expanding and contracting apartment with its myriad hidden spaces had better make someone's theatrical awards list this year. Likewise, Mike Durst's illumination—revealed to its fullest extent as the now married couple's family develops—includes actor-controlled built-in instruments, used hilariously during a confrontational bed scene reminiscent of the Bob Newhart show. Kudos, too, to designers William Hutson and Jonathan Snipes for sound cues—dog barking , toilet flushing, phone rings, and even onstage baby cries—which emanate not from speakers but literally from the intended sources.

Obviously, Klein and Nakamura must age before our eyes. To theirs and Larsen's credit they embody the joys, dilemmas, and tragedies found in Schulner's titular emotion with sensitivity and strength, never relying on makeup gimmickry or amateurish physical affectations. And as their lives unfold, sometimes with only a single line imparting time passage or subject change, we are lovingly swept along with laughter and tears.

"An Infinite Ache," presented by and at the Black Dahlia Theatre, 5453 W. Pico Blvd., West Hollywood. Wed.-Sat. 8 p.m., Sun. 7 p.m. Sept. 10-Oct. 24. (Dark Sept. 15, 16, 24, and 25.) $20. (866) 468-3399.