In this tightly plotted and affecting fourth book (Twelve Tales of Christmas, etc.) from the Utah state legislator, a young man who returns to the small town of his youth must hunt out an unnameable secret from his grandfather's past in order to give his grandmother the Christmas gift of peace of mind. After the death of her husband, Ruth Martin discovered in his journals mention of a mysterious woman named Lillian. Her faith shaken after 55 years of what she believed was loyal marriage, Ruth enlists the aid of her grandson, Will, whom the older couple raised after his parents died. Will has taken a leave of absence from his Wall Street career in order to put his grandfather's real estate business in order, and in every corner of the town he discovers clues to the character of the beloved patriarch, who seemed too good to be true. Yet was he? Siddoway manages to keep the reader guessing at Lillian's identity, and, despite some heavy-handed family-values messages (grandfather died on the Fourth of July; Will's initial love interest is deemed unworthy because she is ""chic and sophisticated and image-conscious""), he knows just where to pull at the heart strings. The novel delivers an uplifting spiritual message while maintaining a level of sophistication in both prose and plot development. Major ad/promo; Random House audio. (Oct.) FYI: Debbie Reynolds will star in a CBS TV film based on this story.