Natalia Osipova and David Hallberg dance in “Giselle.” (Gene Schiavone)

As ballet stars David Hallberg and Natalia Osipova strode onstage for the last of many curtain calls Friday night after their electrifying “Giselle,” with American Ballet Theatre, audience members responded with a little performance of their own. 

A spontaneous chorus of “Happy Birthday” rang through the Metropolitan Opera House, sung by those in the rows around me, because not only do Hallberg and Osipova share a dance partnership that feels like destiny set to music, they were also born on the same day, May 18. And wouldn’t you know that happened to be the date of the only “Giselle” they’re dancing together during ABT’s spring season.

Of course. That these dance celebrities are birthday buddies (a few years apart; he’s 36, she’s 32) only added to the karmic drama of an evening centered on their star-crossed union. Injuries and geographical separation have made them a rare sight together. And then there was the shadow of the terrible fragility of the dancing body. 

Just a few years ago, Hallberg, one of the great male dancers of his generation and an ABT principal, was sidelined for more than two years with a crippling foot injury. Before that happened, he’d discovered a profound artistic affinity with Osipova, a thrillingly unpredictable Russian ballerina renowned for her lightness and high jump. She was formerly with the Bolshoi, and he’d first encountered her when she was a guest artist at ABT. Dancing with her again was a major motivation for his return to the stage.

“I’m very aware of myself performing sometimes,” he told Interview magazine recently. “And I think with her, I become unaware of performing, and I really, in essence, just live.”

Then, in March, a nightmare: Hallberg was finally reunited with Osipova, in a production of “Giselle” with the Royal Ballet, her current home, but he injured himself in the first act and had to be replaced. Was that the beginning of the end for him? How could one know until he was back onstage, with her, with “Giselle”? It all came down to Friday’s performance, with Osipova on the roster as an ABT guest. There were 3,000 hopes in the house that Hallberg would make it through the night.

Come to think of it, the intense but elusive Hallberg-Osipova partnership, marked by physical vulnerability, echoes key details of “Giselle,” with its ill-fated lovers, one who risks her life to dance, the other who’s nearly destroyed by dancing.

“Giselle” is the oldest continually performed ballet in the world, an 1841 masterpiece of the romantic era, but Hallberg and Osipova brought it urgently to life as though it were their own story. Of the countless “Giselles” I’ve attended in more than 30 years of dance writing, this one was most true to the underlying passion and sensuality of the ballet. I saw it anew — and not only that: I felt it.

“Giselle,” after all, is a ballet about the body. This isn’t usually emphasized; Giselle, a peasant, is generally played as chaste and shy, and Albrecht, a count disguised as a commoner, is a proper gentleman. But not so with Hallberg and Osipova. They injected an erotic tone. I’m not talking about anything salacious; they simply made clear, with unforced but decidedly full-bodied energy, that these mismatched lovers shared a sexual as well as a soulful connection. This emphasis is fully in keeping with the ballet, which centers, after all, on sensual urges — the human desire to dance, and the pleasures and perils of that. 

Giselle, as a character, is defined as a girl who loves to dance though she’s in fragile health and really shouldn’t exert herself. Osipova made clear that her Giselle is a free spirit and a sensualist: She gulps air and throws back her head in delight while she’s spinning, and she laughs, heartily and open-mouthed, even during a blazing series of turns. Hallberg has a more unobtrusive style, sleek and pure. If his leaps were somewhat underpowered — was it post-injury caution? — his second-act entrechats, the jumps in place where the feet, in midair, cross back and forth at the ankle, were marvels of flickering speed and control. And when he’s with Osipova, her impulsivity changes him. 

As their village by the Rhine celebrates the wine harvest, Giselle and Albrecht are drunk on dancing, and love. They seem to be one person, deeply connected, eyes locked, every move as they dance together harmoniously coordinated so that their arms hold the same shape, their torsos tilt in unison. When her ailing heart causes Giselle to falter, Hallberg’s Albrecht nearly covers Osipova’s body with his own, as if to transfuse her with his life force. Osipova buries her head in his shoulder in a gesture so intimate, you almost want to look away. Later, after they dance again, he’s the breathless one, kneeling before her, shocked — so it seems — by his own feelings.

In one of the most iconic passages of the ballet, Giselle traverses the stage in a series of hopping steps on pointe, on one foot. She is showing off for Albrecht (and the audience). Yet Osipova sped through these little steps at such a clip, and so weightlessly, she seemed to be flying. It wasn’t just showing off; she brought the racing pace of a lover’s heartbeat instantly to my mind; it seemed she was swept along uncontrollably in response. 

One of the couple’s most poetic moments, however, was eerily still. It came in Giselle’s “mad” scene, where she learns of Albrecht’s double life, and his hidden betrothal, with disastrous results. Osipova paid artful attention to detail here; even her fingers shook. As she’s slowly retracing the steps they’ve danced together, Hallberg offers her his elbow, but she doesn’t take it; they stand side by side, as if a wall of glass separates them. They don’t touch, and it’s heartbreaking. The physical bond they shared has been severed. Finally he grabs her, covering her body again with his, but she dies in the middle of his kiss.

The erotic charge of the first act continued building narrative force in the second act, where Giselle returns as a ghost, one of the vengeful “wilis” who use the pastime that she loved as a weapon, by forcing stray men to dance to death. Mourning in the moonlight at Giselle’s grave, Albrecht becomes one of their victims. Now it’s his turn to be nearly undone by dancing. Yet Giselle — the true romantic rebel, merciful where others are coldhearted — steps in to save him from Myrta, queen of the wilis. (Christine Shevchenko was stunning here, as a Myrta of majestic ice.)

Osipova was no misty spirit; she was a fiery ghost, her mortal vigor not yet drained out of her. Reunited with Hallberg’s Albrecht, dancing again bound them. Echoing through the ages, one felt the hopeful wish of dance artists the world over: the love of dancing as salvation.

“Energy is the only life and is from the Body,” wrote the romantic poet and artist William Blake. “Energy is Eternal Delight.” He would have seen his words take shape in this “Giselle,” whose heroine was not limited by mortality, who pulsed with energy and life force even in her eternal spirit form. Osipova and Hallberg offered a new way to understand this work, drawing on rare chemistry and, undoubtedly, on the thrill of finally creating a world together after a journey through fire. It felt so right that their witnesses responded with energy of their own: standing, cheering, applauding, hurling flowers and bursting into song.