See in text (A Narrow Fellow in the Grass)
The final line contains a multi-layered metaphor. The phrase “Zero at the Bone” describes bone-chilling horror, a zero-degree temperature. It also suggests a state of personal annihilation, of becoming nothing. This final quatrain shows that the snake, personified as a harmless, “narrow Fellow” in the first quatrain, is not a person at all but a threat. The speaker, who loves all creatures, cannot love the treacherous trickster, the snake in the grass, the serpent in the Garden of Eden. Most pressingly, the speaker’s metaphors for the snake fall away, revealing the terrifying reality of the creature. This shift from trust to cold distrust is the poem’s central thematic turn.