The Eighth Deadly Sin — Jessica Mann

"So long as one isn't found out... that's the eighth deadly sin, didn't you know? A man meets a woman at a cocktail party; he takes her out to dinner, the evening ends intimately in his office, they return to their respective homes and partners. They meet again and again. What starts as a casual affair becomes more serious. Then one day the woman fails to appear...

He sets out to trace her. It should be easy -- he knows her name, that she is married, lives in the country, is the author of a sexy novel. Yet somehow she has contrived to disappear from his life completely.