Diana Bishop is a witch who has rejected her magical heritage. She was raised by her aunts Sarah and Emily after her parents were killed by humans who feared their powers. An accomplished historian with a tenured position at Yale University,
Diana is currently pursuing a research project at Oxford. While studying at the Bodleian Library, she catches the attention of witches, vampires, and daemons alike after summoning missing manuscript Ashmole 782, long thought to contain information on the origin of supernatural species. Biochemist Matthew Clairmont, a vampire, is drawn to Diana initially because of the book, but their repeated encounters spark something in both of them.
Matthew leaves Oxford to visit a daemon friend, Hamish, to hunt for a few days. Diana is approached by witch Peter Knox, who is also interested in Ashmole 782 and is even more persistent than Matthew. Diana soon finds herself stalked by Satu, a Finnish witch allied with Knox, and betrayed by her friend Gillian. With no one else to turn to, Diana seeks help from Matthew. He introduces her to fellow vampires Marcus and Miriam and reveals that they are studying the DNA of creatures to learn why all three supernatural species are in decline. Vampires are failing to sire, witches are much less powerful than their ancestors, and daemons are increasingly plagued by mental illness.