Deadly Promise — Mignon F. Ballard

The first victim was her husband. Then his best friend. So Molly Stonehouse had come to Harmony, Georgia, for Christmas -- to discover who in her husband's cheery hometown was a murderer. At the center of the mystery is a secret from the past, an innocent boyish prank that, decades later, is unfolding with deadly precision. Among the joyful hordes decking the hall, someone is poisoning fruitcake and firing gunshots in the snowy woods. Someone who knows why Molly has come home for the holidays. And plans to make sure she doesn't leave...alive.