He (Mark L. Montgomery) and She (Jenny Bacon): two old flames who can’t put out the fire — even if it is just smoke and mirrors.

One of my favorite books about showbusiness is “Making It on Broadway: Actors’ Tales of Climbing to the Top.” In it, well-respected Broadway actors reveal truths about working in professional commercial theatre, from the short-lived thrills to the incredibly demeaning lows.

One chapter, entitled “Sex in the Workplace,” discusses the strange intimacy that comes between colleagues when working in the theatre. Actress Erin Dilly admits that she notoriously falls for her leading man: “There is legitimacy to a showmance. In theatre, you are asked to tell stories, to be vulnerable, and to fall in love with somebody every night … unless you are a robot — and some people become robots — there is residual stuff that is in you when you walk out the stage door.”

Another actress, Sarah Uriarte Berry, simply has this response: “I want to say, ‘Grow up! You are acting. It’s not real.’ Maybe they don’t want to make that distinction. Maybe they are not happy in their personal lives and want to lose themselves on stage.”

Either way you look at it, kissing your onstage lover four times a show, eight times a week for weeks or months on end has strong potential to mess with one’s head, and playwright Sarah Ruhl explores this notion in Stage Kiss, an audience-pleasing romantic comedy receiving its world premiere at the Goodman Theatre.

Actors She (Jenny Bacon) and He (Mark L. Montgomery) are two old flames reunited when they are cast opposite each other in a drawing room drama as — you guessed it — two old flames reunited. She hasn’t acted in over a decade and is eager to please her completely incompetent director (the ever-reliable Ross Lehman doing everything he can with a ridiculous part). He can’t stop thinking about how to get back into She’s pants after all this time — even if She has a nice, pragmatic husband (the hilariously droll Scott Jaeck) with whom she has a teenage daughter (a scene-stealing Sarah Tolan-Mee) and He has a nice, midwestern schoolteacher girlfriend at home (Erica Elam).

As the wonderfully horrid 1930s play-within-the-play takes shape (it’s the kind of play that uses words like “solarium” and every third person is named “Millicent”), He and She’s showmance takes off. After opening night, they extend the showmance into his apartment (which is actually his girlfriend’s) — while still wearing their characters’ costumes. But her husband doesn’t give up so easily: “You fall in love with every guy you’re in a show with,” he says matter-of-factly. “Now let’s go home.”

But she doesn’t — and they soon learn their lesson of what happens when you extend showmances beyond their shelf-life.

Ruhl’s Stage Kiss is made up of the following ingredients: the backstage/onstage dysfunctional romance of Kiss Me, Kate mixed with the backstage/onstage pratfalls of Noises Off peppered with some Private Lives for the camp and costumes.

It’s a very entertaining evening, filled with great one-liners and some genuinely hilarious scene work. The audience seemed to eat it up. But I left with a smile and a shoulder shrug, and essentially forgot about the play moments after stepping outside — much like a showmance disappears as soon as the scenery is struck.

Speaking of scenery, that’s the grandest element of this production: Todd Rosenthal’s work here is filled with wit and theatrical smoke-and-mirrors, elegantly moving between the onstage and offstage lives of these showpeople. I just wish the play itself was as smartly articulate.

“Stage Kiss” plays through June 5 at the Goodman Theatre, 170 North Dearborn St. More info here >