A play-within-a-play requires double duty for a reviewer.  “One Last Kiss,” the play-within-the-play in this theatrical Russian nesting doll, is a painful 1930s melodrama with cartoonish characters and outdated dialogue. (As one character quips, you know a play will be bad when three people wrote it.) “Stage Kiss," however, is a smart new comedy from the poetic pen of Sarah Ruhl, a play with the heart of a poem about the logistics of love and that sloppy, slobbery line between performance and reality.

A mid-career actress known only as "She" arrives unpreprared to an audition.  She spills open her purse and hasn't read up about the show, but the director doesn't seem to mind.  Theater doesn't boast a lot of jobs for women too old to play Juliet and too young for Lady Macbeth, so they're both grateful to have found one another.  She arrives at the first rehearsal to learn the role requires considerable stage kissing (nothing out of the ordinary), and that the leading man is a former lover of hers (not ordinary).  Both or the actors are now partnered - She with a husband in finance and He with a girlfriend in kindergarten (teachin in kindergarten) – so the pair begin to professionally navigate the tricky terrain of pretending to be in love all the while remembering when they were first in love. Soon, the mechanical motions of the kiss trigger the biological emotions of the forgotten flame. Scientists have long shown that the upper lip is one of the most sensitive parts of the body – second only to a lower piece of anatomy – so it’s no surprise that 288 kisses (9 kisses a show, 8 shows a week, and a 4-week run, math courtesy of She’s financial husband) sends the pair into a stroll down Lovers and Memory Lanes.

Todd Rosenthal’s proscenium-stage-within-a-proscenium-stage perfectly illustrates the shifting worlds of performance and reality our star-crossed lovers exist in . Backstage at an unnamed theater, the wooden tiles of the floor intersect reddened brick that bears the faded letters “THEATER.” As the rehearsal process begins, wall pieces descend (and occasionally wobble) to construct the pastelled parlor of the play-within-a-play. When the leading lady and man leave the stage and head to an apartment, hidden windows in the brick illuminate. Reality and performance become just a matter of lighting. While most of his recent designs have been expert domestic sites (i.e. Martha and George’s book-filled home in “Who’s Afraid of Virginia Woolf?” and the transparent tiers of the Weston estate in “August: Osage County”), he proves he can handle what lies out of sight for an audience - backstage rehearsals with yoga mats and high-rise apartments with pull-out sofas.

Kevin, the understudy, is next in the pecking order to lock lips with the actress.  He manhandles her, staring into her eyes like a tiger ready to eat its prey.  His inability to perfect the kiss is attributed to him being “not straight.” In a role that could easily be played as a flamboyant gay light on his feet, Jeffrey Carlson exists rather on stage like a boulder, heavy and clunky with each step. Lightness is left to the Director (expertly played by Ross Lehman), who bounces between his chair and the actor’s sides like a miniature Robert Falls. His fierce encouragement of the actor’s choices and suggestions - hold the cigarette like this, kiss her like this, shake her like this – sent laughs of recognition throughout the opening night crowd.

One thing the director can’t show the cast is the key to a healthy, long-term relationship. In a play with many roles, there is no clear role model for a healthy relationship. A passive-aggressive Midwestern kindergarten teacher can’t find her soulmate, the daughter of an actress and a finance worker walks in on mom schtupping the leading man. Romantic pairings seem to be made at random. X with Y, Y with Z, and Z with QRST. Eventually, one should be work...right?

“Marriage is about repetition,” the husband says to his wife, She. “Romance isn’t about repetition.” Just as an actor must go through the motions each night – whether with the thrill of opening night or the still of an undersold Saturday afternoon matinee – what shines through is there commitment. The rush of an opening night and of a first kiss fade quickly, and the steady rhythms of a four-week engagement or forty-year marriage take center stage.  Whether passion or commitment will rule our lives is a choice left up to each actor on this terrestial stage, but the playwright does reveal one pair that are true soulmates: Sarah Ruhl and the Stage.

"Stage Kiss" plays at the Goodman Theatre through June 5.  Tickets available at: http://www.goodmantheatre.org/