The creators of the movie version of “Dear Evan Hansen,” the Tony-winning musical, felt they had some explaining to do. The smash-hit Broadway show is about a teenager who perpetuates a cruel lie, one that convulses a grieving family. But it has left open-ended a crucial concern: How does an audience empathize with a main character responsible for such gratuitous suffering?

“I just said, ‘Listen guys, the only thing I felt that the show was lacking is, I think he has to come clean,’ ” said Stephen Chbosky, director of the film that opens in theaters Sept. 24. In the stage incarnation, Evan — originated by Ben Platt, who reprises his Tony-awarded performance — eventually confesses to the family that he barely knew their son Connor, whose suicide Evan has parlayed into sympathetic adulation for himself; it all happens after Evan is mistakenly identified as Connor’s best friend.

The rest of the world that has embraced Evan, though, never gets the truth.

“I kept thinking about Evan and his 10-year high school reunion, and I was like, is Evan still pretending that he’s Connor’s friend?” Chbosky said in a Zoom interview. “I became obsessed about that.”

Chbosky’s challenge to the “Dear Evan Hansen” writing team — composer Justin Paul, lyricist Benj Pasek and book and screenwriter Steven Levenson — sets up a fascinating dichotomy between the Broadway and film treatments. It goes to questions of how a story of some psychological sophistication, devised on one platform, might evolve on another. And whether the additional information the film provides should somehow be taken into account when the musical restarts on Broadway on Dec. 11; four days earlier it resumes its North American tour in Greensboro, N.C.

As common as it is to see the physical world of a stage musical opened up on-screen — most recently in Lin-Manuel Miranda’s “In the Heights” and hinted at in the trailers for Steven Spielberg’s remake of “West Side Story,” coming Dec. 10 — few musicals tinker as drastically with script fundamentals as “Dear Evan Hansen” does.

“I was really excited to revisit certain parts of the story that I felt, you know, have shifted for me over time in how I view them and how I think about them,” Levenson said. “It’s something we wrestled with from the beginning: how much forgiveness does Evan deserve, how much forgiveness does Evan get, and balancing our desire to see him held to account for what he’s done. And still survive this ordeal and come out a better person.”

How successfully the narrative expansion works will be judged by moviegoers and film critics, many of whom may be coming fresh to the musical, which arrived on Broadway in the fall of 2016 after a tryout engagement at Arena Stage. (Before it was forced by covid-19 to shutter in March 2020, the show, directed by Michael Greif, had tallied 1,363 performances at Broadway’s Music Box Theatre.) It’s an especially intriguing issue for a work that lacks some of the entertaining assets of movie musicals, such as splashy production numbers or choreography that might allow a cinematographer’s imagination to run wild.

The material, shot on location in Atlanta, feels as if it has more in common with a three-hanky movie like “Ordinary People” than a campy extravaganza like “Hairspray.” “It’s not a musical with a capital M,” observed Chbosky, a best-selling novelist and veteran screenwriter. But it does feature some high-powered Hollywood actors, namely Julianne Moore as Evan’s harried single mother Heidi and Amy Adams as Connor’s more affluent mom, Cynthia Murphy. And at the center of the “Dear Evan Hansen” universe oscillates Platt, whose father Marc Platt is the film’s producer. The elder Platt, an experienced Broadway hand (he is one of the producers of the megahit “Wicked”) also produced the well-received 2016 film musical “La La Land,” with a score by Pasek and Paul.

“There’s something really powerful about getting absolutely fully in his mind and in his eyes,” Platt said of Evan. “That was really exciting to me in terms of the last step of fully realizing this person. And then, secondly, my most exciting thing was that final act and the idea of actually finally getting to see Evan heal in some way and do actual work to heal and to help others heal. It was kind of cathartic for me, just having known him for so long.”

The musical has amassed a rabid fan base, many of them teens and young adults, who post on social media as #fansens, and who will surely engage in heated debates about the changes to the material. A few songs from the Broadway incarnation have been dropped, including the opening number for the mothers of Evan and Connor, “Anybody Have a Map?”; the emotionally charged “Good for You,” and “To Break in a Glove,” a touching song for Connor’s father (played on screen by Danny Pino, best known for his stint on “Law and Order: SVU”).

Other than Evan, the role most transformed is that of Alana, a high-achieving fellow high-schooler and unwitting co-conspirator in Evan’s subterfuge. In the stage version, Alana is a supporting character who perpetually seems to be waiting for her big moment; in the film she finally gets one, in the person of Amandla Stenberg, whose newly written ballad “The Anonymous Ones” tells of Alana’s acute feeling of isolation.

Levenson explained that some of the musical’s more theatrical devices — such as the use of Connor (played by Colton Ryan) as a ghostly presence all through the story — had to be de-emphasized. “So that opened up this really crucial real estate in the story for who is going to be pushing Evan,” he said of Alana. “It felt like, oh this is a great opportunity to dig into her a lot more and to get to push her center stage a bit.”

The intensity of Platt’s Evan is now the stuff of Broadway lore. Evan’s breakdown in the musical’s climactic aria, “Words Fail,” was so operatic in the theater that it unsettled the nerves. For the movie, Chbosky often opted to film the actors singing live, a choice Platt said helped him again hit his emotional sweet spot.

“No matter how beautifully orchestrated or mixed it might be when something is entirely prerecorded,” Platt said, “there is always a level of self-conscious detachment that happens when a song begins. And so the idea of completing that transition fully in a natural way, and just getting to be standing in the dining room singing directly to the Murphys or even in the woods singing to myself, I think there’s something so deeply human about it.”

Platt’s seven-year journey with Evan, from first workshop to final cut, seems to have ended at last; he was 21 when it began and now, turning 28 this month, he’s moved on to a recording and movie career; he’s been cast in Richard Linklater’s decades-long filming of the Stephen Sondheim-George Furth musical, “Merrily We Roll Along,” whose plot unfolds chronologically in reverse. But Levenson, Pasek and Paul may not be done tinkering.

“I don’t think we’ll be changing the music,” Levenson said. “And I don’t think we’ll be changing major sequences, but just little things I would love to play with.”

There’s no denying that audiences have changed since the show began, certainly in the way they respond to Evan’s mendacity.

“The world we live in is so different than the world of even five or six years ago,” Levenson said. “And the idea of lying, the idea of being held to account is so different than the world when we first wrote this show. The idea of truth and reality became a little different. We’re more sensitive to telling lies has consequences.”