In Oxford's Bodleian library, brilliant American historian and reluctant witch Diana Bishop unwittingly calls up an ancient magical manuscript, Ashmole 782, which has been missing for centuries, and finds herself confronted by acclaimed geneticist and vampire Matthew Clairmont, who is determined to get his hands on the book. Diana's determination not to be frightened by Matthew as he struggles to control his predatory instincts around her fuels a dangerous connection between the two of them. When news of the book's appearance spreads throughout the world of daemons, vampires and witches hiding in plain sight among humans, the hunt for the witch who summoned it takes on a deadly intensity.