When we come to discuss the poem's form, we can say that it comprises six verses of varying length, and also employs an irregular rhyme scheme. It tells the story of the poet's dream in which he saw a beautiful unicorn in a forest. He wakes to find a strand of the unicorn's hair on his pillow, and keeps it thereafter.
The poem evokes a dreamy, romantic atmosphere with its smooth phrases and rhymes, the depiction of a still and silent forest, and the central image of the unicorn - a mythical creature and traditionally a symbol of unearthly beauty and purity. The colour descriptions - 'pearly white', 'silver', and so on - also increase the vividness of the whole enchanting scene. However, there is also a note of melancholy as the unicorn seems to regard the poet as an interloper, as though he has no business in a place of such heavenly beauty and calm. This causes him confusion:
My mind was far from clear.
I could not think or speak.
We can see, then, that he is not even able to reply to the unicorn. We can also note, however, that this inability to move or speak can be quite common in dreams, so that this increases the whole dream-like sensation of the piece.
In the final verses, the dreamer returns to the real world; but on finding a strand of the unicorn's mane on his pillow, he keeps it as a memento. Not only this, it brings him comfort in later days whenever he is in misery; it allows him to recapture the feeling of happiness and peace that the dream afforded. Therefore, the dream seems to have been not just a dream, but more akin to a true spiritual experience.