Friday’s nationwide release is a film of the resurrected, Tony-winning “Merrily We Roll Along,” long famous as a notorious Stephen Sondheim flop.

This is a tale where three youthful best buds see their friendships warp and curdle as years pass — only “Merrily” is unique because it’s a tale told backwards. We begin in bile and end in hopeful promise.

This film captures an actual performance with its stars — Daniel Radcliffe, Jonathan Groff and Lindsay Mendez – preserving their roles for posterity,

At a joint press conference, the trio noted how they bonded and remained close through the triumphant Broadway run.

There’s a classic actor’s nightmare: You wake up to find yourself naked, onstage, not knowing lines, much less their part.

Radcliffe, a Tony-winning Best Supporting Actor here, experienced something similar onstage with “Merrily.” Only worse – because it wasn’t a nightmare, it was real.

“Let me tell the story,” he said. “Only once, I screwed up on Broadway. One time! And it was the longest four minutes of my life.

“It happened probably about eight months in. I just suddenly turned to Jonathan as I was doing the song one day. I heard the music do what it did at that moment and I heard myself, like, out of body, saying the WRONG lyrics.

“Realizing that I had jumped to another verse of the song, I was figuring out how I could get back.

“And I remember I just turned to Jonathan and grabbed him and I don’t think I let go for the rest of the song. It’s like,” he said to Groff, “you were the only thing tethering me to the Earth at that moment.

“It only happened once. But it was, truly, the worst moment of my life on a stage. It was real bad but a real incentive to not screw it up again.

“So I came in the next day and made everyone practice with me. And yeah, it made the last four months very stressful. But there we go.

“And you know what? There are worse songs to be singing while you have a mental breakdown. Somebody asked me, ‘Do you think people noticed?’ Oh, yes! The audience would’ve been very aware of how wrong it had gone.”

Radcliffe subsequently rehearsed that song before every performance.

“Knowing Dan,” Groff said, “it made me wanna cry watching him every day practice that. Literally every day multiple times. Every day before he entered on stage Dan is doing the whole song before he went out. We all knew how much it meant to him.”

Added Mendez, “You knew that Dan lost at least seven years off of his life from that 30-second situation.”

“Merrily We Roll Along” opens Dec. 5