There will be four Doublecross missions, one for each of the books. The missions are a different style to previous missions, as they are not in a game format and you need to add the book to your account to complete the whole mission. The missions are centered around solving codes.
This is the first mission, in which you have to solve codes and answer questions.
This is the second Mission, which can involves searching through the Cahill Web for clues. This mission was Admin Sheila L's first mission, and she will be making the next two missions too.
In this mission, we have to hack the Outcast's email account, in order to find out the name of his final disaster.
This is the last and final mission of the 39 Clues series. We have to track down Dan Cahill and get him out of whatever trouble he’s created for himself.