Shadows of Death — Jeanne M. Dams

Dorothy Martin and her husband, retired Chief Constable Alan Nesbitt, go on a trip to Orkney in Scotland to visit an old friend and see some intriguing Stone Age excavations. They realize there's considerable dissension between the archaeologists and the principal donor for the newest dig, a wealthy and abrasive American.

When a more recent corpse is found at the dig, various suspects are named, but there's not enough evidence to bring a case against anyone. Dorothy, always sensitive to atmosphere and the undercurrent of tension pervading the project, has become fascinated by the strong aura of the ancient past that pervades Orkney, and she and Alan launch an unofficial investigation into the murder.