The Sacred and the Profane — Armand Croft

After Andrew MacCrimmon's wife, Karen, leaves him for the sixth and, apparently the last time, he takes up with Claudia Franchini, once known as “Abigail Durant,” a sensuous but shady woman pathologically obsessed with him since their fiery affair, twenty-four years earlier. When Claudia complains she is being stalked by a man named Shally Behr, a gigolo living with a wealthy old woman in her apartment building, MacCrimmon checks him out. He finds that, not only was Behr a person of interest in two homicides, but he is carrying on an affair with Barbara Millman, the wife of the wealthy stockbroker, Marvin Millman. MacCrimmon concludes the pair is planning to do away with Millman, and warns him, but Millman contemptuously laughs it off, a fatal error. When MacCrimmon exposes Behr and Barbara as Millman's murderers, and proves how they carried out this supposedly perfect crime, Behr first wreaks, then suffers, gory revenge. Meanwhile, Karen has divorced MacCrimmon and is seeing a fundamentalist preacher in Portland. When the preacher's wife dies, Karen marries him, but the day after the wedding, she is committed to a mental hospital. MacCrimmon investigates, and finds that not all holy men are holy.