The Cahills are the most powerful family the world has ever known. However, the family is fractured, and the source of its power has been lost. The story begins with the death of matriarch Grace Cahill. In her will she leaves her heirs a choice: they can either receive a million dollars or a clue. The first Cahill to assemble all 39 clues hidden around the world will discover what makes the family so powerful - a reward beyond measure. It's Cahill versus Cahill in a race to the finish, with readers hot on the heels of the main characters, fourteen-year-old Amy Cahill and her eleven-year-old brother, Dan. The story spans 10 adrenaline-charged books, 350 game cards, and an online world allowing readers to play a part in the story and compete for more than $25,000 in prizes.