In medieval Sicily, in the realm of King Roger and his wife Roxana, the arrival of a mysterious Shepherd has spurred rumors and disturbed everyday life. When he interrupts Sunday Mass with news of his strange songs and his worship of an unknown deity, there is outrage; advisors and congregants urge Roger to imprison him as a heretic. But Roxana feels drawn to the newcomer, comparing the power of his radi­ant smile to the sun. Seeking to learn more of the Shepherd’s strange beliefs, Roger resists calls for his punishment and permits him to speak in the cathedral. The Shepherd describes a God whose path to enlightenment is through joy, lust and pleasure – a God “as youthful and beautiful as I am.”

Who is this man? Though his words do not an­swer the mystery, they clearly hove a danger­ous, magnetic appeal for some – including Roxana, whose fascination is tinged with the erotic. He promises an ecstatically charged new freedom, but the worshipers struggle to continue in their disciplined observance of the Mass. Roger, calling for silence, tells the Shep­herd to return for trial that evening. The con­gregation’s stunned reaction of fear and inner conflict seems to feed the Shepherd’s power over them. “Remember,” he warns Roger, “you call for me yourself.”

With the trusted advisor and scholar Edrisi by his side, Roger awaits the Shepherd with fore­boding. Locked in a test of wills and influence, he feels he is losing his kingly influence and even the loyalty of Roxana, who pleads pas­sionately for Roger to show clemency toward the stranger. The Shepherd arrives for his trial and describes himself as a messenger of God who learned his faith in the East, and whose followers are drawn to his smile, singing and dancing. Roger, appalled, denounces the Shepherd as empowered by the forces of hell – a heretic who would lead his followers to perdition.

With the opposing philosophies in sharp relief, a Dionysian dance spontaneously erupts among the trial’s onlookers, led by the Shep­herd. Roxana joins in, and Roger is possessed by a terrifying vision: he feels he is witnessing the disintegration of his own body. When he orders that the Shepherd be captured, his command seems to go unnoticed, and the Shepherd mockingly invites Roger to follow him as well. Eventually everyone except Edrisi joins the dancing followers of this strange new reli­gion – even Roger, spurring the Shepherd to announce that “the King become the pilgrim.”

As night falls on Roger and Edrisi, Roger has been transformed. Describing himself as a va­grant and a beggar – like a wandering shep­herd, perhaps – he no longer sees the physical world or the trappings of statehood as real. He calls out for Roxana, but the Shepherd appears instead, and his words are accompa­nied by the glow of moonlight in a display of seemingly divine power. Bewildered, Roger is unsure of Roxana’s reality when she appears; when she tries to lead him back to their palace, reassuring him that the Shepherd has gone, he does not know what to believe.

Are Roger and his state destroyed or enlight­ened? When Roxana attempts to persuade him to join the Shepherd’s religious following, the Shepherd reappears as the god Dionysus and Roger offers up a sacrifice to him. As the Shep­herd calls out to his believers, Roxana seeks to follow him to “the land of rapture.” They leave Roger in solitude as the dawn breaks. The dying Roger offers himself up to the light of the rising sun.