A reunion at an all-female college ends in a murder. Professor Diana Ellerby is leaving Oxford's last surviving all-women's college and during a reunion with old students, Poppy Toynton is murdered. Lewis and Hathaway's investigation leads them to a connected 10 year old attack on the sister of one of the other old students in which she was attacked during a party at the college and left in a coma. That case has haunted Lewis and, during the investigation, he reaches out to his former DS, Ali McLennan for assistance. As the current murder investigation continues secrets, blackmail and more bodies are uncovered.