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Doublecross is the 39 Clues series that is after the Unstoppable series. It is the fourth arc in The 39 Clues, and there are four books. The authors of the series are Jude Watson, C. Alexander London, Jenny Goebel, and Sarwat Chadda. The series logo is yellow, after the Ekaterina Branch. One card from each book will form The Outcast Master Plan Puzzle


The Outcast was banished from the Cahill family, never mentioned again. For years, he’s been watching, recruiting, waiting for the chance for revenge.  And now he strikes, with a diabolical plan. The Outcast recreates four of history’s most infamous disasters, and gives the Cahill kids just days to stop them. There are innocent lives on the line, but what might be worst of all is the Doublecross that the Cahill kids don’t see coming…

Will Amy be able to take orders from Ian, now that he’s the head of the family? What famous Cahill villain from the past turns out to have an even deadlier brother?  And will Saladin ever get a dish of red snapper again?


Doublecross Book 1: Mission Titanic[]

This book is written by Jude Watson. It was released on 24th February 2015.


Mission Titanic by Jude Watson


At only seventeen years old, Ian Kabra is head of the Cahills, the most powerful family in the world. He has presidents on speed dial, generals at his beck and call. Ian knows he’s an ideal leader and the only man enough for the job.

There’s just one small problem: He’s already messed up big-time. A Cahill from the past calling himself the Outcast has risen to challenge Ian with an impossible test. The Outcast has re-created four of history’s greatest disasters and dared Ian to stop him. If Ian and his allies can’t decipher the Outcast’s hints in time, innocent people will die. Ian’s only chance to beat the Outcast is to track down his former allies, Amy and Dan.

But finding Amy and Dan will demand from Ian an impossible sacrifice

Doublecross Book 2: Mission Hindenburg[]


Mission Hindenburg by C. Alexander London

This book is written by C. Alexander London. It was released on 28th July 2015.


The Cahills are the world's most powerful family, but their strength is being tested. A sinister man calling himself The Outcast has targeted the family and set them an impossible test. He's recreating four of history's worst disasters and challenging the young Cahills to find and stop the tragedies before it's too late. Now, with one disaster behind them, siblings Dan and Amy Cahill and their friends have just days to discover what the Outcast's next move will be.

Their frantic search seems to be pointing toward a terrifying air disaster, the explosion of the Hindenburg airship. But no one travels by airship anymore -- what do the Outcast's cryptic messages mean? The young Cahills must split up and take to the skies to try to find the answer . . . before their whole world comes crashing down.

Doublecross Book 3: Mission Hurricane[]


Mission Hurricane by Jenny Goebel

This book is written by Jenny Goebel. It was released on 26th January 2016.


Thirteen-year-old Dan Cahill and his older sister, Amy, know that a disaster is about to strike the world. They know they are the only ones who can stop it, and they know they may already be too late. The person behind the disaster is their own relative, a man who calls himself The Outcast. He's already re-created two of history's worst disasters, and is only biding his time before he strikes again.

The clues that the Cahill kids have gathered suggest that the Outcast's latest disaster is modeled after Hurricane Katrina. But what city will he target? And how can anyone conjure up a hurricane? Dan and Amy have no answers and very little time to find them. All they can count on is a tidal wave of trouble coming, and only them to stand in its way.

Doublecross Book 4: Mission Atomic[]


Mission Atomic by Sarwat Chadda

The series finale is written by Sarwat Chadda. it was released on 28th June 2016. ​​​​   


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.


The Doublecross missions are quite different from the Cahills vs Vespers and Unstoppable ones, in that they can be played on mobile devices and do not need Unity Player.

The Outcast Master Plan[]

Like every book series, Doublecross will be having a card puzzle forming The Outcast Master Plan Puzzle, or the Doublecross Card Puzzle, with one of the cards in each book containing one piece of the puzzle.


  • It is the second series to have a one-word series title aside from Unstoppable.
  • The logo is yellow, pertaining to the Ekaterina branch, thus completing the Cahill branch colors.
  • Doublecross is the only series where none of the book colors are the same as the series color.
  • The colors of the book covers shares almost the same colors of the books of the third series, Unstoppable.
  • If you look closely at the cover you will see zeros and ones which is binary code for computer. Zero meaning off one meaning on.