A speaker trudges home on a cold autumn day, hungry, badly dressed and lonely, until a memory of someone they love changes everything. They picture that person lying half-asleep in soft light, with green eyes full of a love the speaker says "can never be mine." That line gives the poem its ache: the comfort is real, but it comes from something out of reach.
The middle stanza zooms out to the turning year. Green fades to orange, then black, then snow wipes the colour away. The speaker seems to accept that everything changes and ends. Yet the final lines push back against that. The loved one will keep the speaker warm "through it all," like a wildflower in an "endless Indian Summer," a stretch of mild weather that outlasts the season it belongs to. The mood is wistful and tender, shadowed by loss but held up by stubborn, quiet devotion.