A person sits at a window all day, watching a green meadow, hoping to learn one true thing about their own soul. The speaker gets so absorbed in this search that the world changes without their noticing: by the end, two inches of snow cover the meadow that was green only hours before. The poem seems to suggest that more than a day has slipped away, though the text leaves the exact length of time open.
The mood is quiet, reflective, and a little startled. There is a gentle sense of loss in the "half a day lost" and the vanished green, but the ending turns warmer. The speaker asks where they went and how long they looked for "you," then names that "you" as someone who would never leave: "my very own witness, my here." Judging by the wording, the soul the speaker was chasing is that constant companion, already present all along. The search outward through thought ends with a return to simple presence.