The 39 Clues Wiki
The 39 Clues Wiki

Mission Atomic is the fourth and last book in the Doublecross series. It was written by Sarwat Chadda and was released on June 28th 2016.

Official Synopsis[]


Thirteen-year-old Dan Cahill and his older sister, Amy, are running out of time. An exiled Cahill known as the Outcast has already recreated three of history’s worst disasters, and he’s saved the worst for last. If Dan and Amy can’t find and stop the Outcast fast, he will initiate a full-scale nuclear meltdown. But as Dan and Amy race around the world, they discover something horrifying. The Outcast’s disasters are only a smokescreen to cover up his true plan, a diabolical revenge on the family that betrayed him. Soon Amy and Dan will have to confront a hard truth: sometimes the only way to save the world is to sacrifice everything you love. Even if its your brother.


The prologue starts with Amy in a video chat with Dan Cahill. Amy starts to talk about how The Outcast wants the clues, when Alek Spasky comes in. Gunshots were heard and the Amy's call cuts. Alek Spasky then tells Nathaniel Hartford that Amy is dead.

Three days before that, Amy had an argument with Dan about fighting The Outcast. Amy wanted Dan to be bait, not a fighter. Cara Pierce suggests a face-scan hack.

Look inside the first few chapters.


  • Book Cover Puzzle - (Alternating Letters) - Find the hive​
  • Atomic Page Puzzle - (Alternating Letters) - Killer bees
  • 39+ Pages Puzzle - (Alternating Letters) - Buzz buzz
  • End Page Puzzle(Alternating Letters) - Sinead is returning


  • Like the other last books in a series, the cover logo here is tampered with, as it is on fire, although not broken on the front cover like the other 3. Inside the back cover, it is broken.


The following cards will only be available as digital cards:

Card 353: The Ringleader -This card completes the Outcast Master Plan Puzzle

Card 354: Once a Dweeb...

Card 355: The Loyal Friend

Card 356: The Mentor

Card 357: Captain Kabra

Card 358: Ham It Up!


Mission Atomic - artwork