Loneliness in this poem isn't something that travels. It stays put, clinging to bare tree limbs, grey sidewalks dusted with fresh snow, and red brick walls. The speaker suggests a whole life has rushed past these places, a life with no quiet moment to stop and breathe. It didn't turn out the way the woman wanted, or the way the walls "wanted to feel it."
That woman is named Hattie, and the speaker seems to know her only through the place and the thought of her. The bricks, branches and walks hold her memory and offer it to him. He corrects himself, saying it isn't really her who comes, just the idea of her "still blood." Still, when he takes in that thought, he carries off a little of the loneliness they share.
The mood is quiet, wintry and tender. The repeated "blood red" and the final "blood" link sadness, life and death, while the slow, halting lines feel like someone pausing to remember.