DENVER — As the first brooding chords of the song “Let It Go” arose from the orchestra, a whisper of wonder overswept the audience. And then a mighty sound began.

It wasn’t Elsa.

Oh yes, Caissie Levy, who plays that ice-cursed royal in Disney’s stage adaptation of the hit animated musical “Frozen,” was muttering the first words of the ubiquitous anthem and winding up to blow the house down at the end of the show’s first act.

But the noise was the noise of little girls. Throughout the enormous Buell Theater, at the Denver Center for the Performing Arts here, they — and not a few boys — were already singing along. And when, as the story demands, Elsa’s somber dress magically transformed into a form-fitting, ice blue, crystal-studded gown, they shrieked in admiration. Some even stood, as if in solidarity, to show off the ice blue gowns they too had worn to the theater.

This was completely adorable but also a little strange. How did the dark, neurotic Elsa — along with her younger sister, Anna, and the prince and the ice monger and the reindeer and, yes, the goofball snowman — get here? And what story were they telling in this sometimes charming, sometimes awesome, sometimes lumbering adaptation?