Trapped

I made the mistake of reading what is supposed to be "fact" at the start of an excerpt from Dan Brown's latest novel "The Lost Symbol" - and I am almost hooked but wonder whether it is truly "fact" and if it is, how on earth could Dan (or his wife if she is still helping with his research as was suggested some time ago) know. The fact (paraphrased): In 1991 a document was locked in the safe of the CIA's direction. It is still there and includes refererences to an ancient portal and an unknown underground location. [Of course, I'm thinking Star Gate as opposed to a mere a door]. Where does the portal lead, what does it do, and why is Dan Brown sending Robert Langdon on a mission to "unravel ancient secrets" - what benefit will it provide (besides the obvious ones to the author and publisher)? And when does the book come out?