39 Clues -- Cahills vs Vespers

The Medusa Plot by Gordon Korman

Are you ready to save the world? The bestselling series returns with an adventure spanning six explosive books.
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 had 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 dying. Amy and Dan don't know what the Vespers want or how to stop them. Only one thing is clear. The Vespers are playing to win, and if they get their hands on the Clues... the world will be their next hostage.

This book has been snapped up by our die-hard fans of the 39 Clues series - I haven't even had my turn with it yet - oh well, I guess that is what the holds list is for.