Constantia MacAdams works as a wet nurse at the commodious old house called Spring Gardens, just west of the River Esk. As The Great Unknown opens, the Robert Chambers family is proving to be a handful. There are eight children in the house as well as kindly Mrs. Chambers, who rules the roost and is extremely thankful for Constantia who has come to them from a family connection some years standing. Alliances are constantly shifting and then reforming in this house of "merry children." They're a talkative, playful, mirthful clan.

Set in the 1846, several years before the publishing of Charles Darwin's On the Origin of the Species, Kingman's novel addresses the role that the book Vestiges of the Natural History of Creation played in the formation of the era's views of natural selection. Though it may have just a modest red cloth blinding, the treatise is seen as sensational and wicked. Lady Janet, the Chambers' current houseguest who spies eldest daughter Nina reading it, sees the publication as pernicious and blasphemous. The book claims to be the first attempt to connect the natural sciences into a history of creation and also--shockingly--asserts that humankind is no exception.

Lady Janet argues over dinner that all creation and every kind of creature has come into existence in a perfect and permanent form and not as the results of any "laws of nature." The identity of its author is a mystery, which leads to much dinner-table gossip. Who created it? How had it come into existence? Everyone knows the author, "the Great Unknown," has become the most-kept secret in the world. Jovial Robert Chambers can shed little light on the identity of the author.

Constantia, who narrates much of Kingman's tale, becomes our eyes and ears to the Victorian goings-on. With her mysterious past, it is Constantia, while holding close baby daughter Livia, who offers up a world of struggle after she decides to retrace her father's lineage, first in India and then in England. Constantia loves Spring Gardens and its picaresque surroundings, yet she's drawn to her childhood memories of India. Miss Constantia Babcock always assumed she was the progeny of a lieutenant in the service of the East India Company who was carried off by tropical fever.

Other characters add color. Quarryman Mr. Hugh Stevenson is engaged in a critical operation digging into ancient limestone off an English shore, forty miles south of the mouth of the River Tweed. When he's not digging, Hugh is meticulously reading Vestiges of the Natural History of Creation, pressed upon him by his friend Mr. Darling, the keeper of the lighthouse at the south end of Coquet Isle. Hugh is drawn to the fossils, the spiraled bodies of ammonites and the crinoids: "Even hardest rock wears down to dust washes into the bottom of the sea."

Educated, worldly Constantia is plagued by feelings of illegitimacy ("she's fatherless, nameless, anonymous, in the most literal meaning of the word.") Though the misconduct of her parents took place long in the past before she was born, this disgraceful fact has colored her life. Buoyed by love, she begins her search, her travels eventually bringing her into the orbit of her beloved Hugh. At Seaton Hall, Constantia is transported. She remembers sun-dazzled Dilkusha, her heart's desire, a sunny contrast to the bitter cold of the Northumbrian night and her present difficulties. Later, while Livia sleeps in her bed, Hugh and Constantia revel in their refuge, the private theatre of "their ardent joy."

As the story reveals itself, we are teased by Kingman's use of language - words that locate the Victorians in their place or time, that reveal their relationship before any other evidence is available. Connecting the past to the future, this is a story of a woman who struggles to find an independent place in a world. Part of Constantia's charm is that she pays little attention to what others say about her. Hugh's fossil discoveries allow Constantia to break all the rules, freeing her to go the distance with Livia always in her arms.