She almost vanished. When Emily Dickinson died in 1886, at fifty-five, in the same Amherst, Massachusetts house where she had been born, only a handful of her poems had been published -- most of them anonymously, all of them altered by editors who smoothed her eccentric punctuation and regularized her slant rhymes. Her sister Lavinia, cleaning out Emily's room, discovered forty hand-sewn booklets containing nearly 1,800 poems. Without that act of housekeeping, the most original voice in American poetry might have been lost entirely.

The popular image of Dickinson -- the reclusive spinster in white, the ghostly figure glimpsed through upstairs windows -- is not entirely wrong, but it is dangerously incomplete. She was reclusive, yes. By her thirties she rarely left the family homestead, communicating with visitors through closed doors, lowering baskets of gingerbread to children from her bedroom window. She dressed in white. She gardened obsessively.

But the inner life concealed by that quietness was volcanic. Her poems are compressed explosions: four-line stanzas in common meter -- the rhythm of Protestant hymns -- packed with dashes, capitalizations, and syntactic ambushes that detonate on contact. "I felt a Funeral, in my Brain" describes a psychological breakdown with the precision of a clinical report and the terror of a nightmare. "Because I could not stop for Death" treats mortality as a gentlemanly caller who takes her for a carriage ride into eternity. "Tell all the truth but tell it slant" is a poetics and an epistemology in eight lines.

She read voraciously: Shakespeare, Keats, the Brontes, Elizabeth Barrett Browning, the Bible. She corresponded with Thomas Wentworth Higginson, a literary editor, sending him poems and asking, with characteristic indirectness, whether her verses "breathed." Higginson recognized her genius but could not quite fathom it. He found her, he later said, "partially cracked."

She was not cracked. She was operating at a frequency that her century could not yet receive. Her dashes were not signs of incoherence but a notation for the way thought actually moves -- in leaps, hesitations, sudden reversals. Her slant rhymes anticipated modernist practice by half a century. Her engagement with death, consciousness, and the limits of language makes her a contemporary of Heidegger and Wittgenstein, not of Longfellow.

The woman in white, tending her garden, writing at a tiny desk by a window that overlooked the cemetery, was conducting one of the most daring experiments in the history of the English language. She just happened to conduct it in secret.