While surfing around seeking information about the two authors Preston and Child, I stumbled over their free web-ebook called Hex:
http://www.prestonchild.com/sequel/sequel.htm
However, there is no ending chapter, only ending ideas: their own and the winners of a competition between the readers.
And if you are a fan of the successful pair, you might love to look at the background material to each of their books, including how they work together despite being some 2000 miles apart.
Jorgen