"When seven members of his family were kidnapped by the Vespers thirteen-year-old Dan Cahill knew he was in for the fight of his life. He knew he was up against an impossibly powerful enemy. And Dan knew the odds were that some of his family members wouldn't make it. But even as Dan steels himself to accept these facts, the unthinkable happens. The Vespers capture a blameless bystander, Dan's best friend Atticus."
In Too Deep (The 39 Clues Series #6). "Could Amy and Dan's biggest enemy be . . . a friend? The 39 Clues Book 6 challenges everything you thought you knew about the Clue race. JOIN ANYTIME TO PLAY FOR THE CHANCE TO WIN! The 39 Clues gets treacherous. Book 6 takes Amy and Dan across oceans on the trail of a famous aviator, but they find more than they're looking for. Their enemies are becoming more vicious, and the truths they discover more crushing than ever."