Dickinson opens with a scene so small it could be a joke: a winter room, a worm, and a speaker who isn't sure what to do about it. The worm is "Pink, lank and warm," a faintly unpleasant trio of adjectives in which "warm" makes the creature oddly alive, almost intimate. The speaker's logic is both funny and revealing. "Worms presume," so the worm gets tied "by a string / To something neighboring," and the speaker simply "went along." The offhand tone is the trap. Anyone who ties up a worm assumes the matter is settled.
The poem turns on the understatement "A Trifle afterward." What follows is something the speaker "'d not believe it if I heard / But state with creeping blood." The phrase "creeping blood" puns on the way the creatures move and the way fear feels in the body. A snake "with mottles rare" now surveys the floor, "In feature as the worm before / But ringed with power." The creature seems to be the same one, only promoted. Then comes the shortest stanza, four lines long, which pins down the detail that makes the scene frightening: "That string was there." The speaker's old act of control is still attached, now useless, perhaps even decorative. "Ringed" works two ways, suggesting a snake's coils and a ring of authority.
The conversation that follows is the poem's sharpest moment. The speaker shrinks and tries flattery: "How fair you are!" Dickinson calls this "Propitiation's claw," a strange phrase, since snakes have no claws. The claw seems to belong to the appeasement itself, a polite gesture with a hook in it. The snake isn't fooled. "Afraid," he hissed, "Of me?" and then, in a clipped aside, "No cordiality." "He fathomed me" is a good verb choice, because to fathom is to measure depth, as though he lowered a line into her and found fear where friendliness should be.
The sound does a lot of the work. The snake's passage is wrapped in s-sounds: "hissed," "Secreted," "Slim," "swim." His exit is oddly graceful, "to a Rhythm Slim / Secreted in his Form," as if movement were something hidden inside him and released. The phrase almost describes the poem itself, whose lines are short, uneven and slipping. The rhymes slip too. They begin with the repeated "worm" and the near-echoes of "warm," "presume" and "home," then loosen and drift. In the final stanza they bunch together like footsteps: "flew" and "pursue," "Town" and "down." The poem speeds up as the speaker bolts, keeping "Both eyes his way," running until she is "Towns on from mine."
Then comes the last line, "This was a dream." It is flat, almost bureaucratic, and it arrives with no relief. A dream label should calm things down, but it comes only after the fear has been made vivid, and the creeping blood has already done its work. It also lets the poem say something uncomfortable while keeping a safe distance.
Dickinson never says what the worm stands for, and that openness is part of the poem's power. One reading, an inference from the story's shape, is a parable about whatever we belittle and tie to a post: it may return larger, and our politeness may only advertise our fear. The snake's contempt is aimed less at her terror than at her pretending.
Dickinson lived from 1830 to 1886 in Amherst, Massachusetts, and few of her poems appeared in print in her lifetime. This one shows why readers have kept returning to her. In fewer than forty lines she combines domestic comedy, a fable and a nightmare, and she uses dashes, capital letters and abrupt line breaks to make a small room feel dangerous.