What took ballet administrators so long to rediscover Frederick Ashton’s “Sylvia”? Created for the Royal Ballet in 1952, it left the Royal’s active repertory in the 1960s. In 2004, the Royal finally reconstructed it – and American Ballet Theatre scored a hit with it last year. Monday night marked the welcome return of “Sylvia” to ABT for a four-performance run, where it proved once more that it is a unique and even crucial work in the canon.

Ashton originally created the role of Sylvia for Margot Fonteyn. It was part of the Royal’s enduring effort to incarnate her as a modern balletic heroine as prepossessing as the icons of old. Sylvia is perhaps the most protean ballerina role Ashton made for Fonteyn – or for anyone else, for that matter. It is virtually impossible for a single ballerina to be equally adept in each of the three contrasting acts. Fonteyn could not jump the way ABT’s Gillian Murphy did on Monday night, yet Fonteyn’s style and theatrical intelligence surely compensated.

Young Ms. Murphy is just beginning to manifest the theatrical acumen of a Fonteyn, but overall she did more than commendable justice to the many facets of Sylvia. She cleverly used every possibility the role gave to expand her range. Returning from the hunt, in Act I, her leaps were expectedly galvanic and had a tomboy charm. She inflected these thunderclap jumps with dramatic intention, as well. In her Act I, there was also a girlishness that foreshadowed the lovelorn heroine she was to become. Ms. Murphy manifested an understanding of the physical oppositions and dynamic stillness of the contraposto poses that are every bit as important to this role as any choreographic step.

Ms. Murphy has developed in a way that allows her to articulate her legs with more suppleness and eroticism than before. In Act II, imprisoned by the hunter Orion, she leads a bacchanal to get him safely disabled by drink.

Ms. Murphy is not, however, always at her best at openings. What looked like some tension in her face and neck marred her acting at times on Monday night. But some of her acting, particularly in Act II, was completely persuasive. She was an ideal embodiment of renunciation when refusing the cloths of gold and other blandishments proffered by Orion’s slaves. She was every bit the grand heroine of mythological drama that she needed to be at the conclusion of Act II, when she kneels center stage, pinpointed by a lone spotlight, and appeals to Eros for help.

Ashton had Petipa’s 1890 “Sleeping Beauty” very much on his mind when he made “Sylvia,” as he did when making “Cinderella” in 1948. References to “Beauty” abound in “Sylvia.” Ashton’s attention to “Beauty” also influenced his portrayal of Aminta, the male hero in “Sylvia.” Aminta is a shepherd, but is costumed like an Apollo. Like “Beauty’s” Prince Desire, Aminta is a quintessential danseur noble. There is little attempt to characterize him as a rustic; rather he suggests the archetypal ephebe, the Greek youth just entering adulthood. On Monday night, Maxim Beloserkovsky as Aminta fulfilled Ashton’s intentions very well.

Last year, Marcelo Gomes was ideal in the role, in part because his physique, which tends toward the husky, suggested a note of earthiness. On Monday night, he danced the role of Orion with surging libido and high, capering jumps.

The crucial role of Eros is conceived in “Sylvia” paradoxically. He must maintain majestic repose in his stance (he is immobile for long stretches onstage) and noble authority in his gestures. When he does dance, he is not so much a noble figure as a demi-caractere virtuoso. Eros was danced Monday night by Carlos Lopez, who is the right physical type and was a convincing native of the divine pantheon, but needed to demonstrate more precision and vitality in his dance passages.

Ashton’s introduction of a contemporary flavor to his mythological cosmos is particularly evident in Act III, which takes place outside Diana’s temple. It is meant to suggest Olympus, with numerous appearances by visiting divinities. It is a timeless empyrean, but it also has a suggestion of a Hunt Ball in some London shire, or a costume party in pre-World War II London. Here, too, there’s a flavor of music hall to the flapping elbows of Aminta’s variation, and the hornpipe flavor of Eros’s solo.

In the Act III pas de deux, several strained moments in the partnering made Ms. Murphy and Mr. Beloserkovsky seem like acquaintances rather than lovers. She was marvelously quick and fluid in the fast jumps of her solo, although last year she seemed more at ease with the Ashtonian frou-frou of this act.

“Sylvia” builds to a smashing finale when Diana bolts out of her temple in a fury because Orion has tried to breach the doors to her sanctum, where Sylvia has taken refuge. She vanquishes Orion with a well-aimed arrow, but her rage is calmed. She gives Sylvia and Aminta’s union her blessing afterEros forces her to recall her own love for the shepherd Endymion.As Diana, Carmen Corella seized the tide of this short but stunning role, dissolving from a martial and flinty archetype of female chasteness to an emotion-drenched but still majestic woman mourning a lost love.

Until July 6, Metropolitan Opera House (Lincoln Center, 212-362-6000).