Once Amy and Dan Cahill's choice was simple - take a million dollars or the first of 39 Clues that lead to the source of unimaginable power. Now it's clear that the hunt for Clues is bigger than anything that Amy and Dan could ever have imagined. Innocent people have died, and more will fall if the Cahill power gets into the wrong hands. Now the decision confronting Amy and Dan is excruciating - the choice between the last Clue and one of their lives.