Harriet Vane attends a reunion at her Oxford College and is asked by the Warden to investigate a series of poison pen notes that several members of staff have received. She takes up residence in the college and receives one of these notes herself. In the cloistered environment of the school, there is any number of possible suspects. In the absence of a motive however, it is difficult to determine if the culprit is a member of staff, a student or even if it is a man or a woman. When Lord Peter Wimsey visits the college - as much to see Harriet as for anything else - he agrees to assist in the investigation. What he finds is that one member of the staff had reason to seek vengeance.