Amy and Dan Cahill are the underdogs on the hunt for the 39 Clues. They have no parents, no money, and no one they can trust. Yet they aren't entirely alone—the mysterious Madrigals have been monitoring them the whole time. Are they simply observing Amy and Dan—watching them move from one life-threatening situation into another? Or are the Madrigals laying plans to lure Amy and Dan into their most deadly trap yet?