The speaker joins a crowd to watch a man hanged for robbery, then does something startling: reaches out and touches the corpse. The poem is built from that moment of contact, and it stays quiet and close, without commentary or judgment.
The body feels "cold as silk" and "sleek as a seed." Both comparisons are oddly gentle, even beautiful, which makes the scene stranger. A dead man becomes something smooth and small, like a seed, as if life might still be packed inside it. Then the speaker imagines the heart, "fuddled" and "impossible," as though it has stopped without understanding why. The last image, the teeth that will never fall out, is the most chilling. It reminds us of all the ordinary years this man has lost.
The mood is hushed, tender and unsettled. The speaker never says what he thinks of the punishment, but the details do the arguing for him.