Lewis: Old, Unhappy, Far Off Things (2011)

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.