At a reunion at all female college Lady Matilda's,Poppy Toynton,bossy housemate of principal Diana Ellerby,is murdered.Years earlier Lewis had visited the same college when fifteen-year old Chloe Brooks,visiting her student sister Ruth,had been attacked,supposably by Ruth's American boyfriend Jud Havelock,who disappeared. Chloe went into a coma from which she has only recently recovered but has little recall of that night's events. Lewis visits Ali McLennan,a retired colleague who worked on the Havelock case but she has no leads for him. Then she too is murdered and Lewis discovers that she was blackmailing Poppy for killing Jud. Poppy was also responsible for a hate campaign against several of her former student contemporaries,whose lives suffered as a result. Most of them were present on the night of Jud's disappearance,which Hathaway,tracking down the costumes for the party for that night and using Poppy's video evidence,reconstructs,nailing the killer and their motives.

An American bishop attending a multi-denominational meeting at the heavily Catholic St. Gerard's College dies after drinking poisoned wine but the CCTV footage at her hotel shows that the cowled figure delivering the wine probably intended it for retired policeman Barry Winter,who is also murdered. Father Moreno Mancini is stepping down as college head and the candidates to replace him include staunchly Catholic Brother Blackmore,open-minded Professor Pinnock and free-thinking new broom Caroline Hope,partner of ex-con turned author Al Darrow. The fourth candidate Jeremy Swain becomes the next victim,a note declaring Wild Justice pinned to his chest. Outright rivalry to be Father Mancini's successor is ruled out when it is revealed that one of the candidates committed a murder as a child and was given a new name after serving their sentence. It seems that a relative of the victim has tracked them down and is seeking their own wild justice.

Student Amy Katz is murdered whilst taking part in a clinical trial for anti-depressant drugs, overseen by Dr. Alex Gansa, her psychiatrist following her soldier brother's death in Afghanistan. Amy captivated the other young male volunteers, including love-lorn Adam Douglas and Jack Collins - to the intense hatred of Jack's girlfriend Karen - but Amy was in love with the married Gansa. Several suspicious incidents cause Lewis to investigate the doctor.

Andrea De Ritter, founder of an organization that supports gifted children, is murdered after making a presentation to Zoe Suskin, only fifteen but an Oxford student. That night Andrea had resisted the advances of young student Elmo Woodeson as well as sending a copy of the autobiography of former spy mistress Dame Grace Orde to Zoe's publisher father Leon. She had added inside the book "Who Killed Mary? See Chapter 8." Both Leon and Elmo are killed shortly after and Zoe's tutor Donald Voss is poisoned though not fatally. Suskin had punched Liam Cullen, Andrea's lover, wrongly believing he was having an affair with his wife Judith following a text message to her and indeed sexual affairs, with Andrea at their hub, would seem to motivate the killings. However Dame Grace eventually tells Lewis that Mary, a naive young informant, was sacrificed by her IRA lover back in Belfast in 1987, when Grace was an operative and Liam worked for a pro-Republican lawyer.Revenge on the gunman is the true reason for the killings as he fights to prevent his exposure, though Dame Grace at least has a positive surprise for Lewis.