A painful divorce brings Cassandra James to Cambridge, where she takes up a lectureship in a women's college and moves into her new home, an isolated house deep in the Fens. Suddenly her quiet life is shattered when she discovers the body of her head of department, Margaret, floating in a swimming pool. This death triggers a series of events that threatens everything Cassandra values: her job, her integrity, and her independence. She suspects that Margaret might have been murdered, and she is fearful that she herself might be the killer's next target. Will her skills in solving literary puzzles help her to unmask the assassin? She now has more to lose than she could ever have dreamt: it is her own life she must protect.