A moth lands on the speaker's hand without warning, and that small surprise is the whole scene. The title, "Time to retire," sets the hour: it's late, the working day is done. Then the poem turns the phrase around. The speaker looks at the gray moth and wonders about it, "who works so gray / so late." The moth seems to be a worker too, still going when everyone else has packed up.
The speaker feels gentle curiosity and a kind of kinship. Calling the moth gray, the color of dusk and of dull office days, makes it seem like a tired night-shift worker, and the speaker half sees themselves in it. Nothing is stated outright, so that link is left for us to feel.
The mood is quiet, tender and a little wistful. The short lines mimic the moth's brief, light touch, and the poem ends on "late," leaving us in the dim hour with the speaker and the small visitor.