A young woman is convinced she's living with a murderer among family members, lodgers, and ranch hands in New Mexico.      Serena Mallory came to the huge New Mexico ranch of Castle Rock as a twelve-year-old orphan. She grew up as the ward of owner Dan McIntire. Now in her early twenties, Serena watches the ranch's idyllic summer charm disappear when Dan dies in a riding accident. The night before his accident, she overheard him arguing with someone, and since his death, a series of strange accidents has plagued the ranch. Convinced that Dan's accident was anything but, Serena sets out to find the guilty party.