The title, "Circadian," points to the body's twenty-four-hour rhythm, and the poem seems to move through one day, from noon to midnight. It opens with a strange, almost dreamlike image: a white horse and a house of plague. Together they feel both beautiful and ominous, as if the middle of the day carries a hint of dread. Then the speaker steps in plainly: "here I am."
The middle lines are the heart of it. The more the speaker knows, the more they notice, and that growing attention seems to build as the hours pass. By midnight, the speaker has "turned into myself." That could mean a retreat into solitude, or a kind of arrival at one's truest self. The poem leaves it open.
The mood is quiet, watchful, and a little uneasy. Awareness deepens as the light fades, and the day ends with the speaker alone with their own mind.