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

CHECKMATE

Thirteen-year-old Dan Cahill and his older sister, Amy, are running out of time. An exiled Cahill known as the Outcast has already re-created three of history's worst disasters, and he's saved the worst for last. If Dan and Amy can't find and stop the Outcast fast, he will initiate a full-scale nuclear meltdown.

But as Dan and Amy race around the world, they discover something horrifying. The Outcast's disasters are only a smoke screen to cover up his true plan, a diabolical revenge on the family that betrayed him. Soon Amy and
Dan will have to confront a hard truth: Sometimes the only way to save the world is to sacrifice everything you love.