A brother tells his sister to go to bed, she refuses to be bossed about, he threatens to turn her into soup, and a cook says no. That is the whole plot. Lewis Carroll gives this ordinary nursery squabble the full ceremony of a ballad, complete with a moral at the end. The central idea is comic deflation: a grand threat falls apart when it meets a sister who won't be frightened and a cook who won't hand over a pan.
The brother is introduced as "prudent", which is the opposite of what he proves to be. His first command, "Go and rest your weary head", sounds almost tender, like an older child imitating a grown-up. The sister's reply is far cooler than his bluster. She is "calm", she has a "beaming eye", and she looks at him "indignantly", a lovely contradiction that makes her seem cheerful and furious at once. Her whole defence is two words: "Only try!" She doesn't need to shout, and the brother's authority is gone.
His threats drift in an interesting direction. He begins with a "battered hide" and scratches, but by the third stanza he is talking about "mutton broth", and kitchen language has crept in before he ever goes near the cook. The simile "as easily as kill a moth" is meant to show how strong he is, but a moth is such a tiny victim that the boast makes his rage look petty.
The sound of the poem drives the joke. Each stanza is a tercet on a single rhyme: bed, head, said; hide, applied, replied; wrath, broth, moth. Three lines hammer on one sound with no way out, which suits an argument that keeps going round the same spot. The rhythm is a chant. The opening line, "SIS-ter, SIS-ter, GO to BED", has the bounce of a skipping rhyme, with seven syllables and a stress on every other beat. Later stanzas stretch to a brisker eight syllables, which fits the way the brother sets off at a trot: "Off to the cook he quickly ran." Rhymes like *ran*, *pan* and *can* are blunt monosyllables that clatter like cookware. In the sister's stanza, the long, pompous "indignantly" sits between the plain *eye* and *try*, and the mismatch is funny.
Then comes the brother's politeness. He asks, "Dear Cook, please lend a frying-pan", and the manners are impeccable even though the purpose is murder. His chosen dish, "Irish stew", is a homely, specific name, as if he were reading from a recipe book. The cook's professional question, "What meat is in that stew to go?", draws out the brother's one moment of honesty, and the answer, "My sister'll be the contents!", is wonderfully clinical. "Contents" is a label word, the kind found on a packet, and it sounds odder than any dramatic threat would.
Here the poem's pattern breaks. The final stanza runs to five lines, split into rapid exchanges, and the cook's "Oh" is the shortest line in the poem. It is also a perfect reaction, with a whole raised eyebrow packed into one syllable. It rhymes with *go* and *No!*, so the cook gets the last word, as the sister did in the first half. The boy who opened by giving orders ends by collecting two refusals, one from each woman in the story.
The closing line, "Moral: Never stew your sister", plays on the habit of tacking a lesson onto children's verse. The advice is so obviously unnecessary that it becomes the final joke. Readers who know Carroll from the Alice books will recognise this pleasure in teasing solemn forms.
The poem is slight, but it shows a neat trick. Violence is only ever talked about, never done, and every threat is wrapped in regular rhyme and good manners. The tidier the form, the sillier the menace becomes, and that gap between orderly verse and wild intention gives the poem its charm. It also rings true, because every family knows the sibling who makes enormous threats and hopes nobody calls the bluff.