The son of a reclusive historian finds his mother's drowned body in the tributary of the River Cam that runs through her garden. She is clutching a glass prism. Elizabeth Vogelsang's magnum opus, a book on Isaac Newton's alchemy, is incomplete. Lydia Brooke, a writer friend of the dead historian, returns to Cambridge to the funeral. It is five years since she has seen Elizabeth's son, Cameron Brown, with whom she has had an intermittent love affair that began years earlier.
Cambridge, she discovers, is in the midst of an upsurge of attacks by animal rights extremists. Cameron, who, as a neuroscientist uses animal experimentation, has been targeted. Cameron asks Lydia to act as a paid ghostwriter in the completion of his mother's book, Alchemist. Lydia agrees to the proposal and moves into Elizabeth's strange house, a triangular shaped studio on the banks of the Cam. Soon Lydia finds herself entangled, not only with Cameron, but also with a four-hundred year-old murder mystery, a network of 17th century alchemists and a ghostly figure intent on disrupting her work.