At Oxford University, in the mid-13th century, Regent Master William Falconer (Falconer and the Face of God, 1997, etc.) has undertaken a journey to Conishead Priory on remote Lancaster Bay- -the intent being to study the scientific tomes in the collection of Bishop Grossteste, now belonging to library of the Priory. He leaves just before the unheralded arrival of his friend Ann Segrim and the discovery, at nearby Godstow Abbey, of a murdered young nun. Falconer, guided on foot across the tidal bay by the young son of Ellen Shokburn, longtime worker at the Priory, finds a mare's nest of secrets behind the monastic life of dawn-to-dusk prayers. The immediate puzzle is the whereabouts of books missing from the collection, and librarian Brother Ralph Westerdale provides little help. Prior Henry Ussher, meanwhile, is absorbed in his ambition for higher office and seemingly stunned when the 15-year-old skeleton of Brother John de Landetoft, his onetime rival for the Priorship, emerges from the sands of the bay. Back in Oxford, Ann Segrim has determined to solve the mystery at Godstow Abbey, with the help of Falconer's old friend Constable Peter Bullock--and, despite the autocratic opposition of Abbess Lady Gwladys, she manages to do just that. At the Priory another murder has taken place, and Falconer's physical stamina is sorely tested in the treacherous shoals before he finds answers to murders old and new. More than enough church ritual, shadowy figures, spooky noises, and tidal lore, all couched in stiff and stately prose. Fine fare for lovers of the ecclesiastical; for others, a rather dull slog.