The poem is built from a few quiet images that don't quite explain themselves, and that is part of its effect. A speaker walks home, and the scene slides into something dreamlike: herring "coming out" with a grace as great as the night. The image suggests a shoal of silvery fish emerging, or perhaps the night itself unfolding, and the speaker seems struck by how beautiful and unhurried it all is.
Then the poem turns. Once "the work of the house is done," a "sudden grief" arrives. The judgment here is an inference, but it feels as if busyness has been holding the sadness back, and only in the stillness after the chores can it break through. The mood is hushed, tender, and a little eerie. Beauty and sorrow sit side by side, and the poem never says what the grief is for. It leaves us with the feeling rather than the reason, which makes it feel true to how grief often behaves.