Mission Atomic (The 39 Clues: Doublecross, Book 4)

In the gripping finale of 39 Clues Part VI: Doublecross, thirteen-year-old Dan Cahill and his older sister, Amy, face a race against time to thwart the Outcast, a vengeful exiled member of their family. As he orchestrates catastrophic events from history, Dan and Amy uncover a chilling truth: these disasters are mere distractions for his more sinister plan of revenge. To save the world, they must confront the possibility of sacrificing everything they cherish.