At the reading of their grandmother's will, Dan and Amy Cahill are given the choice of receiving a million dollars or uncovering the 39 clues hidden around the world that will lead to the source of the family's power, but by taking on the clues, they end up in a dangerous race against their own family members.

Amy and Dan Cahill have been located once again, this time in the company of the notoriously unreliable Alistair. Spies report that Amy and Dan seem to be tracking the life of one of the most powerful fighters the world has ever known. If this fearsome warrior was a Cahill, his secrets are sure to be well-guarded.

Amy and Dan are hot on the trail of the fourth Clue, but their ruthless relatives will stop at nothing to eliminate them from the competition. Their hunt leads them to an ancient city that has been a hotbed of Cahill activity for centuries. The clock is ticking for Amy and Dan.

"Are some secrets better left buried? As Amy and Dan track the next clue to a remote corner of the world, they make shocking discoveries about the source of the Cahills' power and the mystery of their parents' deaths. And as the threat of the mysterious Madrigals grows real, one of the clue-hunters makes the ultimate sacrifice. Amy and Dan have to decide how much they're willing to risk, and what they are fighting for. Can they avenge their parents...

Amy and Dan Cahill face their greatest challenge on their quest to find the thirty-nine clues, but in order to discover the secrets of their lineage they will have to make a choice that could impact the world's future.

Throughout the hunt for the 39 Clues, Amy and Dan Cahill have uncovered history's greatest mysteries and their family's deadliest secrets. But are they ready to face the truth about the Cahills and the key to their unmatched power? After a whirlwind race that's taken them across five continents, Amy and Dan face the most the difficult challenge yet -- a task no Cahill dared to imagine. When faced with a choice that could change the future of the world,...

"The Black Book of Buried Secrets" lays bare each hidden fact, concealed strategy, top agent, lost founder, secret base and hushed-up scandal of the Clue hunt. This complete guide to the Cahills contains information on all five branches, including the notoriously elusive Madrigals.

One belief has sustained fourteen-year-old Amy Cahill and her younger brother, Dan, on their hunt for the 39 Clues: they are the good guys. But then a shocking discovery about their parents shatters everything Amy and Dan think they know, dividing the two siblings for the first time ever. When Dan disappears in a country of more than a billion people, Amy has to make a terrible choice - find the next Clue - or find her younger brother.

The shaow of a man in black has followed 14-year-old Amy Cahill and her younger brother, Dan, on their worldwide search for 39 Clues that lead to a great power. Amy and Dan know the man in black has tried to kill them. They know he is a Madrigal, a member of the most secretive and terrifyng group hunting for the Clues. Amy and Dan have run hard and fast, but they can't escape the man following them. And now, in the wake of a terrible tragedy,...