Act One

A pianist dressed in formal attire walks across the stage to the piano. Fog and changing lights indicate that the audience is being transported to an otherworldly place. A voiceover explains that, on February 9, 1964, the Pleasantdale High School Glee Club – known as The Sound of Plaid – was on its way to the club's first big gig at the Allegheny Monongahela Valley Civic Center. Unfortunately, a school bus filled with girls from Our Lady of Harrisburg, on its way to see the American TV debut of the Beatles on "The Ed Sullivan Show," crashed into The Sound of Plaid's bus. The Our Lady of Harrisburg students were fine... but not The Sound of Plaid.

There's thunder and lightning. The cast, wearing white dinner jackets, walks through the audience from the back of the house, chanting and carrying candles ("Deus Ex Plaid"). The Plaids realize that they're back on Earth after being suspended in limbo for decades. Since they're in a theatre, they obviously need to perform, but they haven't sung in so long that they're nervous about it. Some of them want to leave, but Mr. Bodine insists that they've gotten the chance of a lifetime, and they can't walk away from it. Miss Fairfax adds that they only have two hours to complete their mission. After finding their old equipment, the Plaids start to come around. The voiceover wonders what happens when unfinished lives are cut shortL perhaps they wander forever, coming back to the world of the living to provide harmony and to support arts programs. The Plaids get ready for their concert; Mr. Bodine and Miss Fairfax remind them that, if they stop the show for any reason, they'll be stuck between the world of the living and the world of the dead forever. During the concert, Mr. Bodine conducts, and Miss Fairfax assists by turning pages and making sure the Plaids are professional. They start the show as a group ("Three Coins in the Fountain").

Mr. Bodine introduces himself as the assistant principal of Pleasantdale High School. Miss Fairfax introduces herself, too; she was subbing for the music teacher on the day of the crash, so she's just here to help Mr. Bodine. Sparky then comes forward to introduce the Plaids. They never got to do this concert while they were alive, so this is their chance to do the concert that they would have done if they had lived. The Plaids quickly step forward, one by one, to state their names. They are clearly uncomfortable on stage and try to get themselves together in the next umber ("Gotta Be This or That / Undecided").

The Plaids try to determine if it's going well, as they start to feel more comfortable. Francis thanks the audience for letting them do this concert. When Francis opens a formal wear catalogue, Gilda is overcome with emotion because they were killed before they got to pick up their tuxedos and concert gowns. Lilith dedicates the next number to anyone who's been to a prom ("Moments to Remember").

As their memories come back, the rest of the Plaids get emotional, as well. Mr. Bodine reminds them that they need to keep going with the concert and hurries them along to the next number, which also serves as a way to cheer them up; Miss Fairfax explains that they are performing with plungers instead of microphones because they rehearsed it in a broom closet ("Crazy 'bout Ya Baby").

Afterwards, Gilda and Jinx stumble through banter while Mr. Bodine and Miss Fairfax put the plungers back. They try to talk about love with some of the other Plaids, but none of them can even say the word. Gladys says that they were all too busy with school and extracurriculars to have time for love, especially with Mr. Bodine drilling them for their college entrance exam. The Plaids and Mr. Bodine then illustrate the drills ("The Osterizer School of Harmony Theory").

Once they're done goofing around, Miss Fairfax encourages them to sing an actual love song. Sparky has one in mind, and the Plaids dive in ("No Not Much"). During the applause, the Plaids experience some physical difficulties: Jinx has a nosebleed and Lilith has an asthma attack. Miss Fairfax tends to the wounded, but the show must go on or The Plaids will be stuck in limbo. This threat is heightened by a lightning strike that blows out the power. Mr. Bodine and two students leave to look for flashlights and an emergency generator.

With Miss Fairfax helping sick students, the only students who are healthy enough – and reliable enough – to keep the show going are the twins, Smudge and Corrine. They're not crazy about the idea, but not having much choice, they take over emcee duty. They show the audience a suitcase that is filled with the only things that they were allowed to take with them after their death: props, the bass charts and their record collection. Smudge tells the audience that, when he and Corrine were little, their parents opened a diner with insurance money from an accident. Their sitter was off on Wednesday nights, so the two of them hung around the diner, waiting for the jukebox lady to give them the old records that people weren't listening to anymore. Smudge and Corrine would obsess over the records and the jukebox itself. They show the audience the album covers that they used to make, hoping that they'd have actual records to sell in them one day.

Just then, the lights come back, revealing that Mr. Bodine and Miss Fairfax are necking, and that the other Plaids are in mild chaos. Nevertheless, it's time to get back to the show. The Plaids explain that, because they didn't have experience with love themselves, they attached meaning to the next song by thinking about their teachers and imagining those teachers' first names were Perfidia ("Perfidia").

Next, it's Jinx's turn for his part of the show, but he's afraid that he won't remember it. Francis reminds him how it starts, and Jinx performs his solo amazingly ("Cry"). Smudge then tries to do his bit, but he feels sick, so Corrine takes over ("Sixteen Tons / Chain Gang").

Mr. Bodine and Miss Fairfax acknowledge the work that the Plaids have put into the club. No matter how busy they were, nights and weekends were devoted to The Sound of Plaid. Mr. Bodine even made up business cards for them. The Plaids explain that, had they been around longer, they would have been happy to work at the audience member's private functions – weddings, anniversaries, Bar Mitzvahs, etc. ("The Catering Drill / She Loves You"). Energized, The Plaids go calypso for their final number of the act ("Caribbean Plaid").

Act Two

The Plaids return to find three ladders onstage – they assume that the crew forgot to remove them. Some of them sit on the ladders while others take stools or spots on the edge of the stage; they get back to the show, aware that time is growing short ("Sh-Boom").

Mary Agnes shares some news articles about the Plaids while the students remove the ladders. Tony and Betty then tell everyone about the time that they met Rosemary Clooney and Perry Como and tricked them into watching their performance ("The Golden Cardigan / Catch a Falling Star / Hey There / Mambo"). At the end of the song, the pianist nonchalantly gets up and walks offstage. Mr. Bodine explains that the pianist is on his union break. Cliff is pushed to the piano and plays a well-known favorite. They then bring an audience member up on stage to perform the melody line with Cliff ("Heart and Soul").

The pianist comes back onstage. Jinx and Sparky, who are stepbrothers, and Mitzi, their foreign exchange student, share what Sunday nights at their house used to be like; the family was always fighting, but they stopped at 8 pm on Sundays for "The Ed Sullivan Show." The Plaids recreate the show, with Mr. Bodine serving as Ed Sullivan. The Plaids recreate a car commercial ("Mercury") and then go into a number that they might have performed on "The Ed Sullivan Show" ("Lady of Spain").

Mr. Bodine explains that, while the Plaids can be silly, they take being Plaids very seriously. To demonstrate this, The Plaids put on their official Scottish Plaids Clothes ("Scotland the Brave"). An usher brings a large box to the stage; in it are the tuxedos and formal dresses that they never got to wear. The Plaids realize that, with these clothes, they could have plaid anywhere ("Shangri-La / Rags to Riches"). Mr. Bodine tries to get them to set up for the finale, but none of the students move; they want to stay, and they figure that, if they don't finish the song, they won't have to go back. Miss Fairfax reminds the Plaids that, even though their lives were short, they did a lot of good. Moreover, their music will last forever, even though the Plaids themselves have died. Mr. Bodine backs her up. Everyone makes his or her decision to finish by performing the final number ("Love Is a Many-Splendored Thing"). When the song is over, the cast is in a golden glow; then the lights go dark. A moon appears before silhouettes of the Plaids appear against the moon and they rise up to heaven.