Another fast-paced, action-packed, adventure novel churned out by Rick Riordan & Co. This is more of a back story to the whole 39 clues series, with about 3/4th's of the book taking place before Amy and Dan's time.
We start off with Gideon Cahill stumbling upon a "serum" which enhances one's abilities to almost superhuman standards, but fearing his "friend" Damien Vesper wants to steal it for his own good, he divides the ingredients among his four children, Luke, Katherine, Thomas and Jane, so that none of them have the entire serum, but if put together they can shape the entire future civilization.
But Gideon dies while trying to protect his work, his pregnant wife and kids escape and go their separate ways to make their mark on the world. Before she leaves, Gideon's wife Olivia, takes his ring off his body before it falls into Vesper's hands; the ring supposedly is very dangerous and carries a terrible secret. After that, the ring is passed down from Cahill to Cahill over several generations, all the time fighting to keep it from the Vespers, until it is given to Amy and Dan.
Apparently the 39 clues series was supposed to end after the 10th book, where they had found all 39 clues, but due to popular demand, they decided to continue with the books by introducing the Vespers into the picture. The plot device is glaringly obvious with nary a mention of the Vespers until the 10th book, but it works.
The Vespers are ruthless and aren't above murdering two kids (judging by all the YA books out there,is anyone
these days?) for a gold ring with a secret. The book is a roller coaster ride with never a dull moment. The authors manage a good job of continuing the story without making it look like parts of it was written by four different people. Recommended, but read the other ten first (if you haven't already) before picking this up.