Twenty years after their son, Matthew, drowned in an accident near their home, noted opera conductor Sir Gerald Asherton and his wife, Dame Caroline Stowe, who retired from the opera stage after Matty's death, have an eerily similar tragedy to face: The body of their daughter Julia's estranged husband, Connor Swann, of whom they've remained inexplicably fond, has tumbled from the Hambledon Lock. But Connor's death, as Superintendent Duncan Kincaid and Sergeant Gemma James (All Shall Be Well, p. 19, etc.) soon realize, was anything but accidental, and someone among the circle of mourners must be feigning grief- -unless his killer was his widow, who takes sharp issue with the descriptions of her mother (``everyone liked Con'') and the English National Opera staff (``a lovely man'') and calls him a ``bastard.'' Dividing the labor of interrogating the suspects--Gemma takes an afternoon at Brown's Hotel to enjoy an impossibly English tea with opera wardrobe manager Tommy Godwin, with Anglophilic Texan Crombie piling on the scones and clotted cream and coy remarks about prewar detective fiction--the two veterans of Scotland Yard's Homicide Squad patiently unearth the secret Connor died for and predictably disturb the dust on Matty's grave. Though Gemma sagely tells Tommy, ``This isn't a detective novel, for heaven's sake,'' it's as tidily plotted and neatly written as the genuine article.