Description:

Day of Doom is the sixth and final book in the Cahills Vs Vespers subseries of the 39 Clues series of novels. in this book, Amy and Dan are in a race to prevent a terrible Vesper plot. Amy and Dan Cahill are orphaned siblings who gradually discover many secrets about their family. After a quest to uncover a Cahill family secret that pits different branches of the family against each other, now they have to contend with a different and very powerful enemy.
The Cahill family is united now, but a new enemy, the Vespers, challenge them. The Vespers have now kidnapped seven members of the Cahill family and are demanding bizarre ransoms. These strange objects from around the world seem unrelated but hard to find.
Amy and Dan race across the world to deliver the ransom and prevent the Vespers from harming their hostages. Then, they discover that the objects demanded as ransom are not unrelated, but are vital pieces in a horrible Vesper scheme that can harm the world.
Now, Dan and Amy have to worry about more than just their own family. If the Vespers are allowed to complete their scheme, it could harm millions of people. So, they now have to come up with a way to stop the Vespers from carrying out their plans.