Four months after being shot Morse returns to work and witnesses a pageant, held to mark nine hundred years of history, disrupted by two events. The first is when feminist Kitty, daughter of prospective MP Barbara Batten, sprays beauty queen Diana Day with red paint, the second when an unknown man falls to his death from a roof. Initially deemed a suicide he has a host of fake identity cards and has scrawled a message in a motel notebook, D DAY FRIDAY 98018. When Bernard Yelland comes to Oxford in search of his runaway step-daughter Frida, Morse believes that FRIDAY actually reads FRIDA Y whilst D DAY could also signify Diana Day though a diversion from these mysteries is provided by the burglary of the Wolvercote Trove from the local museum. The dead man is a London-based private detective, Pettifer, who is not above blackmailing his clients and is possibly involved in the burglary though this is later disproved. Morse meanwhile works out the significance of the figures and exposes secrets of the great and good to discover who killed Pettifer and Frida.