The setting is a medieval castle, the time is January 20, the eve of the Feast of St. Agnes. Madeline, the daughter of the lord of the castle, is looking forward to midnight, for she has been assured by "old dames" that, if she performs certain rites, she will have a magical vision of her lover at midnight in her dreams. Madeline believes in this old superstition and prepares to do all that is required, such as going supperless to bed.
On this same evening, Porphyro, who is in love with Madeline and whom she loves, manages to get into the castle unobserved. Madeline's family regards Porphyro as an enemy whom they are ready to kill on sight. The presence of many guests in the castle helps make it possible for Porphyro to escape notice. By chance he meets Madeline's old nurse, Angela, who is his friend; she tells him of Madeline's quaint superstition. At once the idea of making Madeline's belief become reality by his presence in her bedroom at midnight flashes into his mind. He assures Angela that he means no harm and she reluctantly agrees to help him. She leads him to Madeline's chamber where he hides in a closet.
Madeline soon enters and, her mind filled with the thought of the wonderful vision she will soon have, goes to bed and falls asleep. The ritual she has performed produces the expected result; her sleep becomes the sleep of enchantment and Porphyro, looking as if immortalized, fills her dreams.
After Madeline falls asleep, Porphyro leaves the closet and approaches her bed in order to awaken her. His whispering does not stir her; her sleep is "a midnight charm / Impossible to melt as iced stream." He picks up her lute and plays it close to her ear. Suddenly her eyes open wide but she remains in the grip of the magic spell. Then "there was a painful change, that nigh expell'd / The blisses of her dream so pure and deep." She now sees Porphyro, not immortal as in her dream, but in his ordinary mortality. The contrast is so great that Madeline even thinks that the human Porphyro is on the point of death. She wants her visionary Porphyro back again. Her wish is granted; the operations of magic are powerful enough to enable Porphyro, "beyond a mortal man impassion'd far," to enter her dream vision and there they are united in a mystic marriage.
When the magic visionary state comes to an end, Madeline expresses her fear that Porphyro will abandon her, "a deceived thing; — / A dove forlorn and lost with sick unpruned wing." Porphyro, who now addresses her as his bride, urges her to leave the castle with him. "Awake! arise! my love, and fearless be, / For o'er the southern moors I have a home for thee."
The two leave the castle undetected and go out into the storm. That night the baron and all his guests have bad dreams, and Angela and the old Beadsman both die.
In The Eve of St. Agnes, Keats uses the metrical romance or narrative verse form cultivated extensively by medieval poets and revived by the romantic poets. Scott and Byron became the most popular writers of verse narrative. Keats' metrical pattern is the iambic nine-line Spenserian stanza that earlier poets had found suitable for descriptive and meditative poetry. Because of its length and slow movement, the Spenserian stanza is not well adapted to the demands of narrative verse. It inhibits rapidity of pace, and the concluding iambic hexameter line, as one critic has remarked, creates the effect of throwing out an anchor at the end of every stanza.
Keats clearly was not very interested in writing lively narrative in The Eve of St. Agnes. The story is trifling and the characters are of no great interest. Porphyro is an idealized knight who will face any danger whatsoever to see his lady love, and Madeline is reduced to an exquisitely lovely and loving young lady. Keats is interested in celebrating romantic love; romantic love is literally a heavenly experience, and for its culmination Keats puts his lovers temporarily in a heaven that is realized through magic. The Eve of St. Agnes is, in part, a poem of the supernatural which the romantic poets were so fond of employing.
The Eve of St. Agnes is a heavily descriptive poem; it is like a painting that is filled with carefully observed and minute detail. In this respect, it was a labor of love for Keats and provided him with an opportunity to exploit his innate sensuousness. Imagery such as "he follow'd through a lowly arched way, / Brushing the cobwebs with his lofty plume," all of stanzas XXIV and XXV describing the stained glass window in Madeline's room and Madeline's appearance transformed by moonlight passing through the stained glass, stanza XXX cataloguing the foods placed on the table in Madeline's room, the lines "the arras, rich with horseman, haw, and hound, / Flutter'd in the besieging wind's uproar; / And the long carpets rose along the gusty floor," show Keats' picture-making mind at work. The poem has to be read with scrupulous attention; every detail makes a distinctive contribution and even though much of what is in the poem is there for its own sake, everything at the same time makes its contribution to the exaltation of romantic love. Some critics view the poem as Keats' celebration of his first and only experience of romance. It was written not long after Keats and Fanny Brawne had fallen in love.
Readers have been struck by Keats' use of contrast in The Eve of St.Agnes; it is one of the chief aesthetic devices employed in the poem. The special effect of contrast is that it draws attention to all the details so that none are missed. Keats deliberately emphasizes the bitterly cold weather of St. Agnes' Eve so that ultimately the delightful warmth of happy love is emphasized. The owl, the hare, and the sheep are all affected by the cold although all three are particularly well protected by nature against it: "The owl, for all his feathers, was a-cold." The hatred of Madeline's relatives for Porphyro, for whatever reason, highlights the love of Madeline and Porphyro for each other. Age is contrasted with youth; the poverty and self-denial of the Beadsman are contrasted with the richness of the feast that Porphyro prepares for Madeline.
All the senses are appealed to at one time or another throughout the course of the poem, but, as in most poems, it is the sense of sight that is chiefly appealed to. The most striking example of Keats' appeal to the sense of sight is to be found in his description of the stained glass window in Madeline's room. This window was "diamonded with panes of quaint device, / Innumerable of stains and splendid dyes." Madeline is transformed into a "splendid angel" by the stained glass as the moonlight shines through it:
Full on this casement shone the wintry moon,
And threw warm gules on Madeline's fair breast,
As down she knelt for heaven's grace and boon;
Rose-bloom fell on her hands, together prest,
And on her silver cross soft amethyst,
And on her hair a glory, like a saint:
She seem'd a splendid angel, newly drest,
Save wings, for heaven: — Porphyro grew faint:
She knelt, so pure a thing, so free from mortal taint.
Keats put a stained glass window in Madeline's room in order to glorify her and put her firmly at the center of his story.
The concluding stanza of the poem raises a problem. Why does Keats have Angela, who had helped Porphyro and Madeline achieve a happy issue to their love, and the Beadsman, who had nothing to do with it, die at the end of the story? Their death does not come as a total surprise, for earlier in the poem Keats implied that both might die soon. Possibly Keats, looking beyond the end of his story, saw that Angela would be punished for not reporting the presence of Porphyro in the castle and for helping him. Death removes her from the reach of punishment. Keats may have used the death of the Beadsman, to whom he had devoted two and a half stanzas at the beginning of the poem, to close off his story. And so the Beadsman "For aye unsought for slept among his ashes cold." Keats needed a good concluding stanza to his poem, whose main characters disappear from the scene in the next to last stanza, and so the lives of his two minor characters end with the end of the poem.