In Too Deep is the 6th book in the 39 Clues series. This time around Amy and Dan are off to Sydney, Australia. This was the last destination their parents visited while on their quest. Amy and Dan visit their Dad's cousin Shep who is a pilot and surf bum in Sydney, to see if he has any clues as to what their parents discovered or where they may have visited. He helps them trace some of their parents steps, which of course puts them in great danger at the hands of the other Cahill family members.
Irina informs Amy that the only person who can tell her who killed her parents is herself. She begins having increasing flashbacks and starts piecing the events of that night together. She is afraid to tell Dad what she remembers, which causes some tension between them.
Our history lesson in this book is about Amelia Earhart. Her final journey involved stops in several of the areas Amy and Dan visit and of course they discover Amelia was a Cahill.
The stakes are getting higher and the violence continues to escalate. One of the Cahill family members even dies in this book, which was a bit of a shock. Amy and Dan have been told from the very beginning that they shouldn't trust anyone. They are now even questioning if their au pair, Nellie, is working for someone involved in the quest.
This was another entertaining story. My son and I have enjoyed learning some history while following the Cahill children on their quest. Once he finishes his assigned summer reading for school I'm sure we will start the next book in the series.