The 39 clues. Cahills vs. Vespers

When Dan and Amy deliver the last ransom to Vesper One, they learn the objects are part of a plan that will harm millions of innocent people. The two siblings and their friends race to stop Vesper One before he destroys the world.

Amy and Dan Cahill learn that there is a traitor in their midst who's giving information to the Vespers. They race against time to uncover who it is before the next hostage dies.