Blake begins by speaking over the heads of his own age. "Children of the future age," he calls, asking them to read this "indignant page" and understand that "in a former time / Love, sweet love, was thought a crime." The anger is stated at once, and it is aimed at a society that treats affection as an offence. What follows is a short story showing how that offence gets manufactured: a young couple meet and delight in each other, and the girl goes home to be frightened by her father.
The story moves between two climates. The first is the lovers' world, an "age of gold" that is "free from winter's cold," where youth and maiden stand "naked in the sunny beams." The light is "holy," and it acts like a gentle stagehand, removing "the curtains of the night" to reveal the garden. Nothing here is hidden or shameful. One small line is easy to miss: "Parents were afar, / Strangers came not near, / And the maiden soon forgot her fear." Her fear is only mentioned as it disappears, and it vanishes when no one is watching. The poem suggests that this fear is something the watchers bring with them.
The second climate arrives with the father, and the colours change. "To her father white / Came the maiden bright." Brightness belongs to her and to the morning, while whiteness is his, the white of age and drained colour. Then comes the poem's key collision: "his loving look, / Like the holy book / All her tender limbs with terror shook." "Holy" was earlier used for sunlight. Now it describes scripture, and the two kinds of holiness clash. Blake never says the father speaks or strikes. His look is called "loving," yet it carries the weight of a sacred text and is enough to make her shake. All she has done, as far as we are told, is kiss someone and agree to meet again. The terror seems learned rather than natural.
The last stanza complicates the picture. The father addresses her by name for the only time, "Ona, pale and weak," and his speech is full of his own fear: "Oh the trembling fear! / Oh the dismal care / That shakes the blossoms of my hoary hair!" Calling white hair "blossoms" is oddly tender, and the flowers are trembling. He is not a simple tyrant. He seems caught in the same system that frightens his daughter, and perhaps he enforces it because it frightens him. The poem ends on his cry, and we never learn what happens next.
The form carries much of this effect. After an opening quatrain of two couplets, the poem settles into five-line stanzas, mostly a rhymed pair followed by a rhymed triplet ("sweet / meet / sleep / deep / weep"). The short, lilting lines sound almost like a nursery song, which suits a tale about young people and keeps the telling deceptively simple. The last line of each stanza stretches longer than the ones before it ("Had just removed the curtains of the night"), like a breath let out. In the final stanza that longer line becomes the father's gasp. The closing rhyme of "fear," "care" and "hair" is slightly uneasy to a modern ear, which fits a stanza where the harmony breaks down. The gentle sound makes the content more disturbing, because the song-like rhythm carries on while the girl trembles. Even the lovers' arrangement is set against sadness: they will meet when sleep "waves o'er heaven's deep, / And the weary tired wanderers weep." The night is already tinged with grief before anything has gone wrong.
The poem's significance lies in where it places the crime. Love is not what is wrong here. The wrong is the fear taught to a child, so that she reads her own joy as guilt. Blake makes the argument through contrasts of light and book, bright and white, song and shaking, and he never lectures. The title's indefinite article, "A Little Girl Lost," makes her one case among many. She is lost not by wandering off but by being taught to tremble at the thing that made her happy.