The Medusa Plot

Thirteen-year-old Dan Cahill and his older sister, Amy, thought they belonged to the world's most powerful family. They thought the hunt for 39 Clues leading to the source of that power was over. They even thought they'd won. But Amy and Dan were wrong. One by one, distress calls start coming in from around the globe. Cahills are being kidnapped by a shadowy group known only as the Vespers. Now Amy and Dan have only days to fulfill a bizarre ransom request or their captured friends will start dy