A proem is a short introduction, in verse, to the matter and meaning of the rest of the poem. Some published editions of the poem do not make a division between The Proem and The Dream. The Proem is lines 1 through 290, and The Dream is lines 291 through 1334, the end of the poem. In The Book of the Duchess, the poet is introduced in the first person. He has difficulty getting to sleep and has not slept, he says, for eight years. He reaches for a copy of a "romaunce" (a word describing the Metamorphoses of the ancient Roman poet Ovid) and reads the tale of King Seys and Queen Alcyone.
The king goes across the sea on a ship, and a storm arises and drowns all aboard. Queen Alcyone, anxious at home and awaiting his return, sends to the east and west looking for him. Until she knows the king's fate, she will not eat bread. Distraught, she prays to Juno to send her a dream that would tell her of the fate of Seys. Juno immediately sends Alcyone to sleep, and he sends a messenger to Morpheus, the god of sleep. Morpheus is to go to the Great Sea (the Mediterranean) and enliven the king's drowned body with his own spirit. This reanimated corpse he should send to Alcyone to speak to her and show her he has drowned.
Juno's messenger goes to the dark valley where the gods Morpheus and Eclympasteyr sleep. He rouses Morpheus, who does Juno's bidding and conveys the dead Seys to speak to his wife Alcyone. In her dream, Alcyone sees Seys at the foot of her bed, and he tells her that he has died and that she must find his body by the sea and bury it. He also tells her not to remain in sorrow too long. He adds that she was his true love in life. With "To lytel while oure blysse lasteth" [too little while our bliss lasts] (line 211), he leaves her, echoing a theme of this and other poems in Chaucer's love-poetry oeuvre. Alcyone awakens, and Seys is gone.
The narrator now reflects how helpful it would be to have the god of sleep come and give him much-needed rest himself.