Are some secrets better left buried? As Amy and Dan track the next clue to a remote corner of the world, they make shocking discoveries about the source of the Cahills' power and the mystery of their parents' deaths. And as the threat of the mysterious Madrigals grows real, one of the clue-hunters makes the ultimate sacrifice. Amy and Dan have to decide how much they're willing to risk, and what they are fighting for. Can they avenge their parents - or are they following their fatal path?