The graphic novel adaptation of the mega-bestseller that launched a global phenomenon!Minutes before she died Grace Cahill changed her will, leaving her decendants an impossible decision: "You have a choice - one million dollars or a clue."Grace is the last matriarch of the Cahills, the world's most powerful family. Everyone from Marie Curie to Harry Houdini is related to the Cahills, yet the source of the family power is lost. 39 Clues hidden around...