From the back cover: the race is on to find 39 clues that safeguard a great power, and fourteen-year-old amy cahill and her younger brother, dan, are shocked to find themselves in the lead. The search seems to be taking ...From the back cover: the race is on to find 39 clues that safeguard a great power, and fourteen-year-old amy cahill and her younger brother, dan, are shocked to find themselves in the lead. The search seems to be taking them to vienna, and they hold a coded piece Of Mozart's sheet Music That's key to finding the next clue.