A guilty thing surprised

"The Nightingales were a happy couple with few problems or worries in their twilight years. The sudden and mysterious murder of Mrs. Nightingale, however, leads Chief Inspector Wexford deep into their mysterious and hidden lifestyles."@en
"Even the dead have something to hide. The discovery of Elizabeth Nightingale's broken body in the woods near her home could not have come as a bigger shock. Called in to investigate, Chief Inspector Wexford quickly determines that the Nightingales were considered the perfect couple, wealthy, attractive and without an enemy in the world. However, someone must have been alone with Elizabeth that night in the woods. Someone who hated, or perhaps loved, her enough to beat her to death. The case seems straightforward. But Wexford soon learns that beneath the placid surface of the Nightingales' lives lie undercurrents and secrets no one ever suspected."
"The Nightingales were always a very happy couple. But someone had reason to quarrel with Elizabeth. Someone who was alone with her in the woods on a dark September night. Someone who loved or hated her enough to beat her until she died. The Nightingale case seemed straightforward enough on the surface. But Detective Chief Inspector Wexford soon discovered that beneath the placid surface of the Nightingale's lives there were undercurrents and secrets no one had ever expected - container."