Well, the plot’s ordinary enough: a lovingly raised lower-class teenage seamstress (Louise) meets a dashing young artist (the poet Julien), and runs off to the glam big city (Paris) to live in bohemian-style sin with him, leaving her traditionally minded parents bereft. But it’s what French composer-librettist Gustave Charpentier did with this seemingly simple scenario that transformed Louise into a first-rate (though unjustly neglected) opera.

First, he refined and expanded the story so as to reflect universal human themes that resound even today — though we now label them differently: like “rebellion against authority,” “empty-nest syndrome,” or “urban renewal.” Then, in words and music, he fleshed out some truly believable and sympathetic characters — making it hard for the opera-goer to take sides. The tragedy here, even though nobody dies, is a ruined family. And the shallow, hedonistic “freedom” that wins in the end rings as only a hollow triumph.

And the music: Charpentier wrote in a kind of “French Verismo” style, reflecting the overblown drama, vocal techniques, and emotional intensity of Italian masters like Giuseppe Verdi. But he also paid heavy chromatic and sonic tribute to the influence of his German contemporary, Richard Wagner — though filtered through a French sieve. No matter what its influences, it’s deliciously rich and sparkling music — though the sparkle peters out whenever the going gets sad or contentious.

On Friday’s opening night, Maestro Emmanuel Villaume demonstrated full command of this complex score, drawing precise, juicy and emotionally potent playing from his superb Spoleto Festival Orchestra. The Westminster Choir — aka “the world’s finest opera chorus” — shone, too – especially in the big third-act “party” scene. Many of their singers also got to strut their solo stuff, in over 20 bit-parts: the first time most of them got to do named roles in a full-fledged grand opera production. With voices like those on board, no wonder the choir sounds so incredible.

The lead roles were all well-filled. As heroine Louise, soprano Stefania Dovhan was a wonder. As the opera unfolded, she morphed convincingly from a giddy, moonstruck teenager into a far more worldly creature. She even pulled off an impressive vocal shift in the process: her light, girlish tones shifted into richer, more sensual sonorities as she switched worlds (and priorities). As her hero Julien, tenor Sergei Kunaev delivered the full goods, with riveting, testosterone-driven intensity and a ringing top end.

Louise’s unnamed parents – the ultimate losers – were also superbly rendered. Her clueless daddy — magnificently sung by bass Louis Otey — was the evening’s most pitiable character, delivering some of the opera’s most emotionally devastating singing. Her mother, done by mezzo-soprano Barbara Dever, was the classic mom-from-hell — though she knew the real score better than anybody else. The remaining significant roles fell to baritone Stephen Morscheck (the Ragpicker) and tenor David Cangelosi (Noctambulist). We also got great work from assorted sopranos Anne-Carolyn Byrd (Camille), Andriana Churchman (Irma) and Marjorie Elinor Dix (Gertrude).

Director Sam Helfrich and set designer Andrew Cavanaugh Holland conspired to create a convincing and (intermittently) fantasy-ridden stage environment. From the dull, musty confines of Louise’s family flat to the opulent splendor of Paris (think “City of Lights”), the ambiences fit the going scenario. Sets melted ingeniously into each other from one scene to the next. Lighting director Aaron Black also had a lot to do with the evening’s wide-ranging moods and effects. Costume designer Kaye Voyce stuck mostly to imaginative variations on period dress themes, except in the big party scene.

That very episode revealed several instances of wacky, even surreal inspiration all-around. The high point came (for me) when a bevy of six young ladies suddenly shed their stodgy seamstress garb in a choreographed striptease, revealing short, sequined skirts underneath. They then delivered a sort of dry-land parody of water ballet, producing the evening’s supreme moment of comic relief.

Aside from a few very minor opening-night disconnects between pit and stage, I heard no real performance flaws to speak of. Villaume’s meticulous cuing kept even his many rookie bit-part soloists in lock-step with the score. My only real gripe was some slow and tedious going in the final act: Charpentier could’ve made his point with less in several spots.

With this production, Spoleto has again achieved what it has done so well over the years: dusting off obscure operatic treasures, and giving them the kinds of performances that reveal their greatness to us — and the world.