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!

As a member of the most powerful family history has ever known, 13-year-old Dan Cahill has been shot at, kidnapped, and even thrown into a pit with a deadly snake. He’s survived it all due to luck, smarts, and his older sister, Amy, who always sticks by his side. Now Dan and Amy are facing their greatest threat yet, an enemy who has found a way to use the source of the Cahill family power against them.

The blockbuster series continues with a Cahill family member from the past bent on revenge! Who is the Outcast, and why is he threatening the lives of innocent people? Book 3 reveals a shocking secret that will send Amy and Dan - and the world - reeling.

The 39 Clues is unstoppable! The bestselling series returns with an adventure spanning four explosive books and a website that places listeners right in the action.

The 39 Clues is unstoppable! The best-selling series returns with an adventure spanning four explosive volumes and a website that places listeners right in the action.

The Cahill family has a secret. For five hundred years, they have guarded the 39 Clues - thirty-nine ingredients in a serum that transforms whomever takes it into the most powerful person on earth. If the serum got into the wrong hands, the disaster would rock the world. So certain Cahills have always made it their mission to keep the serum safe, buried, locked away. Until now. Thirteen-year-old Dan Cahill and his older sister, Amy, are the latest guardians of the Clues. They think they've done everything right, but a tiny mistake leads to catastrophe.

A Clue found in Book 3 sends Amy and Dan jetting off to find out just what's behind the fierce rivalry between the Tomas and Ekaterina branches of the Cahill family. Was a Clue stolen from the Tomas branch? Where is it now? And most important, can Amy and Dan get their hands on it before their rivals do? It's a wild race that will take Amy and Dan deep into the bowels of the earth... and right into the hands of the enemy.

The race is on to find 39 Clues that safeguard a great power, and 14-year old Amy Cahill and her younger brother, Dan, are shocked to find themselves in the lead. The search seems to be taking them to Vienna, and they hold a coded piece of Mozart's sheet music that's the key to finding the next Clue. But tailed by a pack of power-hungry relatives, Amy and Dan can't see if they are sailing toward victory - or straight into a deadly trap.

When the hunt for the 39 clues leads 14-year-old Amy Cahill and her younger brother, Dan, to Japan, their only chance to find the third Clue seems to lie with their unreliable uncle, Alistair Oh. Will they be foolish enough to make an alliance? With a Clue on the line, Amy and Dan might not have a choice. But in the Cahill family, trusting your relatives can get you killed.

Calling all Cahills! Announcing a 39 Clues Superspecial adventure - the gang is back, and called to investigate one of their own: Sinead Starling.