Madeline is a young noblewoman determined to observe the superstitions of St. Agnes Eve, which dictate that fasting and silence will grant her a dream of her future husband. Surrounded by lively suitors at a raucous celebration, she remains detached and spiritually untethered from the physical world around her. Her deep belief in the old magic puts her in a trance-like state that blurs the line between sleeping and waking.

Porphyro is a passionate youth deeply in love with Madeline. Because of a severe feud with Madeline's family, his presence in the castle puts him in immediate, mortal danger from the other guests. Driven by physical desires that run counter to Madeline's spiritual focus, he takes daring risks and enlists help to hide in her bedchamber.

Angela is Madeline's elderly nurse and an old acquaintance of Porphyro. She is weak in body and highly anxious about religious convention, constantly worrying over her impending mortality and her soul's passage to heaven. Despite her intense fear and her explicit disapproval of Madeline's pagan rituals, she agrees to help Porphyro secure his love.

The Beadsman is an elderly professional person of prayer. He spends his nights in the bitter cold, doing penance and praying for the souls of others. Isolated from the loud celebration happening inside the main hall, his quiet religious devotion provides a sharp contrast to the youthful passion driving the central characters.