Curiosities opens with a present-day amateur historian, Anne, who describes her unexpected discovery of five seventeenth-century manuscripts that, astonishingly, tell the same strange story from vastly different points of view. The five manuscripts spin this tale: after the Plague descends upon a village in England, two small children, Joan and Thomasina, are the only survivors. They bond tightly with each other and with a woman living in the forest nearby, who discovers and cares for them. When people return, the woman, as the lone adult alive, is accused of witchcraft, and the children are separated. Joan is taken on as a maid in the local manor house, and through her intelligence and skill becomes a companion to the fascinating Lady Margaret Long. Thomasina, sent on a sea voyage to Virginia, adopts boy's clothing and navigates life as a man named Tom. Tom and Joan find each other as adults and fall in love, but are discovered together, naked, by a young clergyman. Shocked and horrified, he believes there is but one explanation for Tom's state: Joan must be a witch. Desperate to save both himself and Joan, Tom runs as far away as he can, to the North Pole. And so it falls upon Anne, the contemporary historian, to piece together these interlocking stories, discover the fate of the lovers, and add her own layer of "truth" to a history and time period when there were no labels for who Tom and Joan might truly be.