The New York Times bestselling series. On the hunt for the 39 Clues, Amy and Dan Cahill uncovered shocking information about their past - from what happened the night their parents died to the shattering discovery about their family branch. But the biggest secret of all remains behind Grace Cahill's alternate will. Now, Amy and Dan are about to discover a long-hidden secret of the Cahills - a secret so dangerous that people died to protect it. Will this be the end of them? Or just the end of everything they think they know?

Rick Riordan is the author of the New York Times #1 best-selling The Lost Hero, the first book in the Heroes of Olympus series. Kids across the country voted him Author of the Year for that book through the Children's Book Council in association with Every Child a Reader. Rick also penned the New York Times #1 best-selling Percy Jackson and the Olympians series: Book One: The Lightning Thief, Book Two: The Sea of Monsters, Book Three: The Titan's Curse, Book Four: The Battle of the Labyrinth and Book Five: The Last Olympian. The first two books in his Kane Chronicles, based on Egyptian mythology, The Red Pyramid and The Throne of Fire, were New York Times #1 best sellers as well. Rick lives in San Antonio, Texas, with his wife and two sons.