It is a golden evening of high summer in July 1990. Robin Timariot has set out that morning on what he has planned as a six-day tramp along part of Offa's Dyke. At the close of his first day's walk he encounters an  elegant middle-aged woman who seems strangely out of place among the sheep and gorse of Hergest Ridge. They exchange only a few words of conversation, but their talk is enigmatic — and unforgettable. A few days later, at the end of his walk, Timariot returns home to learn from the newspapers that, just a few hours after their meeting, the woman, whose name was Louise Paxton, was raped and then murdered, along with an artist, Oscar Bantock, who lived near by. A man is swiftly charged and convicted of the crime, but a string of inexplicable events begins to convince Timariot — and others — that all is not what it seems. Timariot, fascinated by Louise Paxton's memory, is drawn irresistibly into the complex motives and relationships of her family and friends, searching against his better judgement for the secret of what really happened on the day she died. The closer he gets to the truth, the more hideous and uncertain it seems to be. And far too late he realizes that it may threaten many powerful people. So much so that anybody who uncovers it is unlikely to be allowed to live.