If you’re a regular theatergoer you may notice a discreet sign in the lobby when you show your ticket at the door. A slip of paper inserted in your program catches your eye, “In this evening’s performance of Giselle, the role of...” Your heart sinks: an understudy.

No one wants to hear that a cast member in any production is unable to perform, especially not when it’s due to injury. In ballet, where the success of a pas de duex depends on the correct pairing of dancers, an understudy can be devastating. Happily, this was not the case in the American Ballet Theater’s Tuesday evening performance of Giselle. Opening the second act in the place of principal dancer Gillian Murphy, soloist Simone Messmer captivated the audience as Myrta, queen of the wilis. Messmer’s sheer grace and fluidity throughout her solo was hypnotic, drawing the audience into Myrta’s restless world. Adolphe Adam’s dynamic score seemed to expand and contract with Messmer’s phrasing, hypnotizing the viewer to forget about Myrta’s wicked purpose until the wilis, spirits of unmarried maidens, reappear.

The groundwork laid out before intermission, however, allows the drama in Giselle’s second act to reach an emotional peak. Set along the Rhine in the Middle Ages, Giselle (Julie Kent) and Albrecht’s (Jose Manuel Carreño) romance is surrounded by the bright colors of the corps de ballet in celebration of the grape harvest. The carefree attitude permeates the music, costumes, and dance, and though Giselle and Albrecht make a beautiful couple, their love and therefore their movement is innocent and uncomplicated. That is not to say the first act is technically inferior. Certainly Giselle’s iconic hops on pointe through center stage are impressive, but Kent makes a clear distinction between the Giselles in the two acts. The living Giselle is free of emotional complexity, she is simply in love.

In the second act Giselle is destined to take her place among the wilis. They trap any man they encounter and force him to dance to death to avenge themselves. Isaac Stappas as Hilarion falls victim to the wilis and successfully created the illusion of weakness while executing a striking series of leaps and turns. Repeatedly forming a stark diagonal line across the stage, the wilis are a powerful force both beautiful and deadly.

When Kent takes the floor this time her new demeanor radiates throughout the audience. Her entire body transforms as Giselle’s desperation to save Albrecht manifests in chaos, then, calmer sadness. Kent truly seems to be of another world. She skims the floor and plays with the music’s haunting melody in every detail of her dancing, captivating each audience member’s attention so that the grand Metropolitan Opera House feels like an intimate theater. With Carreño as a partner Kent’s movement is never interrupted, her limbs lengthening into exquisite arches in the space. The most breathtaking moment occurs when she’s lifted high over his head, her chest and legs reaching ever upwards as if supported by the air itself. Carreño’s solos are a thrilling visual contrast. He keeps Albrecht grounded and human but demonstrates enormous power, springing from the stage to hang in the air. Who could blame Giselle for falling in love?

The oldest continually-performed ballet, Kevin McKenzie’s staging remains true to Jean Coralli, Jules Perrot, and Marius Petipa’s Giselle to delight and amaze all in attendance. One discreet audience member even broke from his trademark austerity into enthusiastic applause (don’t worry, Prince, it’ll be our secret).