Amy and Dan Cahill know their family is big, but they don’t realize how big until their grandmother Grace’s funeral. Relatives arrive from all over the world by special invitation. In Grace’s last will and testament, she issues this challenge:

For your inheritance, you may have the first of thirty-nine clues. The first team to successfully put together the clues, which are scattered across the world, will discover the secret of Cahill power and become the richest, most important people in history. Or you may take one million dollars in cash right now and walk away.

Amy and Dan take the challenge! Soon, they are catapulted into a dangerous round-the-world race for the thirty-nine clues. They will explore every continent, and delve into the strangest, darkest chapters of world history to find the secret origins of their family. Other teams will try to eliminate them by any means necessary, because in this treasure hunt only one team can win, and there are no rules.