39 Clues, The: The Cahill Files: Silent Night

The year is 1914 and war is raging in Europe. Eager to win glory for the Lucian branch, sixteen-year-old Rupert Davenport (Ian Kabra's ancestor) sneaks off to France to join the fighting. But the reality of battle is unlike anything Rupert imagined. Even if he survives the bullets and explosions, he'll have to face an even deadlier threat: the Vespers, the Cahill family's rivals who are plotting a dangerous scheme behind enemy lines.

Yet just when Rupert is about to lose hope, Christmas Eve arrives, and he witnesses something that changes everything he thought he knew about war, and his own family. Is it a holiday miracle? Or a twisted game designed to destroy the Cahills?