The christmas murder game

The Christmas Murder Game is a mystery novel by Alexandra Benedict about a woman, Lily Armitage, who returns to her family's manor, Endgame House, for an annual Christmas game after a 21-year absence. The game, which involves solving 12 riddles to find 12 keys, promises the winner the deeds to the house and the truth about the murder of Lily's mother years ago. However, when a snowstorm traps the estranged cousins inside with no way to contact the outside world, the game turns deadly and Lily realizes she must not only win the prize but also survive the escalating murders.