Backstage at Me and Juliet, a long-running Broadway show, the company prepares for another evening performance. Sidney, an electrician on the show, waits for help from another technician named Bob, but Bob is nowhere to be found. Jeanie, a member of the show’s chorus, was expecting him, too (“A Very Special Day”). When she admits to Sidney this isn’t the first time Bob has stood her up, a few others chime in, wondering why she’d want to go with a guy like Bob. Jeanie explains how their relationship started (“That’s the Way It Happens”).

When Bob finally arrives, Sidney, annoyed by Bob’s lateness, mentions that Jeanie was looking for him. He asks if Bob would ever marry her. Bob laughs, calling Jeanie a “sweet kid,” and promises he’ll never get married, saying the institution is a trap that women use for financial gain. Sidney’s annoyance turns to anger, and he calls Bob a baboon. Bob furiously grabs Sidney by the collar and chokes him until a few of the company members stumble on, including Jeanie. Bob immediately changes his tone and charmingly tells Jeanie about a piano he’d seen for sale. He picks her up and sets her down on a desk, but soon has to take her down because the Assistant Manager, Larry, needs to use it. While the chorus rehearses, Larry sings of his unrequited love for Jeanie (“That’s the Way It Happens” Reprise).

The head stage manager, Mac, is making the nightly rounds when Charlie, the lead actor of Me and Juliet, storms in, complaining about Dario, the production’s music conductor. Charlie blames Dario and his orchestra for playing so loudly that people can’t hear his singing. Dario threatens to quit over having to work with Charlie. To keep Dario on the show, Mac has been sending him single flowers with forged love letters from an anonymous admirer, known as the “gardenia lady,” who has been watching Dario from the audience. Content to play for a secret admirer, Dario agrees to play tonight’s show.

Lily, who plays “Juliet” in Me and Juliet, tells Mac she’s arranged to take her vacation in August. Larry tells Jeanie that leads require a second understudy during the summer months. Though she doesn’t consider herself much of an actress, Larry thinks she should try out for the role because the extra weekly pay could help her afford the piano she’s been eyeing. She laughs at his remembering such a minor detail from their previous conversation, and the actors are called to places. While conducting the “Overture,” Dario looks out for his special admirer, sniffing his gift gardenia passionately.

At the show’s start, the title character, “Me,” played by Charlie, sets the scene and introduces the characters, including Don Juan, Carmen and Juliet, played by Lily (“Opening of Me and Juliet”). “Me” describes just the kind of love he has for her (“Marriage Kind of Love”). Backstage, Bob and Sidney busily change lamp colors on a light bridge above the action on stage. Comparing his situation to the main character’s, Sidney tries to remember how he felt before getting accidentally engaged to his wife, Josephine. Bob identifies more with Don Juan’s character, who is being seduced by Carmen, and he sings along with the show (“Keep It Gay”).

Later, Mac shares the stage when Sidney needs to fix some lights, but Larry also needs it to see Jeanie for a second Juliet understudy audition, all while Mac seeks a potential replacement for the part of Carmen. Sidney agrees to share the stage with Larry, while smugly knowing that Larry has had a crush on Jeanie for a long time. Mac strongly advises Larry against getting involved with a girl in your own show, saying it’s a rule he’d never break.

Charlie brings in actress Betty Lorraine, whom Mac has called the object of his affection. The choreographer and the producer, Mr. Harrison, observe as Betty expertly reads through Carmen’s seduction scene and performs a number from the show (“The Audition: Keep It Gay” Reprise). When she books the part, Betty gives Mac a big, grateful kiss, but he responds coldly. Ruby tells Betty about Mac’s strict rule about dating girls in his show. Betty decides she’ll take the job – and get Mac to break his rule.

With Larry watching, Jeanie begins Juliet’s song timidly, so he stops her. With surprising skill, he thoughtfully explains how Juliet is a strong, passionate character, perhaps more so than Carmen, because Juliet is the one who is actually in love. He continues to give Jeanie direction, describing how to overcome her fear of the smartest people in the theatre – the ever-changing audience (“That Big Black Giant”). In the midst of directing her, Larry notices Jeanie looking at him a certain way and is flustered when she wonders aloud how it is you can be in the same show with someone for so long without ever really knowing them at all. Larry shakes it off and sets her up to try the song out again, as Juliet on the balcony (“No Other Love”). While she practices, Bob approaches the stage to watch, but mocks her from behind. When Jeanie notices, she stops the song, deflated, and leaves. As the stage lights go dark, Bob grabs Larry’s arm and refuses to let go. He threatens Larry, saying that if he crosses the line of stage manager and understudy with Jeanie, Bob will kill him. Bob throws Larry onto the ground and walks off, leaving Larry alone on stage again.

In the stage door alley, members of the chorus gossip about Larry and Jeanie and speculate what will happen when Bob finds out. Betty arrives, and Mac – fervently sticking to his number one rule – greets her with a professional tone that comes off as awkwardly formal. Knowing his inner turmoil, Betty goadingly flirts with him. Ruby, the company manager, catches them dancing together and Mac leaves to start the show. Ruby is left wondering if being in front of an audience every night has anything to do the peculiar personalities of show people (“That Big Black Giant” Reprise).

In their dressing room, Betty and Jeanie discuss Betty’s romantic life, and Mac calls the five-minute warning to places. As they finish getting dressed, Betty passionately muses on what a great thing it is to be an actress (“It’s Me”) before making her way to the stage. Jeanie rushes to put her dress on when Larry arrives and helps her out. They decide they have to tell Bob about being together, and they kiss before Jeanie runs onstage.

Above the stage, Sidney and Bob sit with the lights, waiting for Act I to end. Sidney admits he has never cheated on his wife. Suggesting she may be cheating on him, Bob calculates how long he’s gone at night. Sidney furiously warns him to stop and, unable to hit Bob because of their position in the rafters, resorts to telling him about Jeanie and Larry, and points out the two sharing a kiss below them. Suddenly, a spotlight, controlled by Bob, shines on both of them during the last number of the first act. Betty, performing center stage, tries to continue her solo without being lit by her usual spotlight. Almost stuck in the grip of Bob’s control, Jeanie crosses the stage in his spotlight, unable to escape in front of the audience, when suddenly a sandbag plummets from above the stage and hits the prop tray out of Jeanie’s hands. Terrified, the performers go on with the ending of the act. Finally, Mac orders the curtain to drop.