A surprising twist brings Amy and Dan back to New England for their first mission on U.S. soil since the beginning of the Clue hunt. But being close to home is anything but a comfort. The siblings have learned that there's a mole in the Cahill organization.... And the traitor is one of their closest confidantes. However, this betrayal is overshadowed when Amy and Dan make an even more devastating discovery: the truth about the Vespers' real plan. Burdened with this terrifying information, Amy and Dan are forced to ask an impossible question: Is it more important to save the hostages...or stop the Vespers?

International best seller David Baldacci pens the stunning conclusion to Cahills vs. Vespers! David Baldacci is the author of 23 books for adults, each of which has become both a national and international best seller.

Never turn your back on the Cahills.... The most powerful family history has ever known returns with a vengeance in The 39 Clues: Doublecross! Confidential until August 2015!

At only seventeen years old, Ian Kabra is head of the Cahills, the most powerful family in the world. He has presidents on speed dial, generals at his beck and call. Ian knows he's an ideal leader and the only man for the job. There's just one small problem: He's already messed up big time. A Cahill from the past calling himself the Outcast has risen to challenge Ian with an impossible test. The Outcast has re-created four of history's greatest disasters and dared Ian to stop him.

Amy and Dan have managed to rescue one of the Cahills kidnapped by the Vespers, but the remaining hostages are still in peril. Their search for the next ransom item leads Amy and Dan to Turkey and then to Italy where a visit to the site of an ancient disaster changes everything. The Vespers are far more dangerous than the siblings ever imagined and, even worse, it looks like they have an undercover mole posing as a Cahill. Amy and Dan have to face the biggest decision of their lives with nowhere to turn... and no one to trust.