If you are talking about the books "found" and "sent" then the third book is already out. It's called "sabatoged." It's a good series, I have read it before, and I do recomend it.
it has already come out. :)
Margaret Peterson Haddix's third book in the Missing Series will come out in July 2010. It is called Sabotaged. I think it will be about they get found
Sabotaged, the third book in the Missing series is due on August 24 2010
august 2010
The 5th book in the Missing series by Margaret Peterson Haddix has been out since September 2012.
December 11,2011
The 5th book come out September 4th of 2012 and the book after that come out sometime in 2013.
TornThe book will come out August 23, 2011.
The fourth book came out on August 23, 2012.
The third book in the series will be named The Mark of Athena and it will come out October 2, 2012.
the third book passion comes out on June 14 2011
It has already came out. Its title is Sabotaged.