Chris Shelton spent 27 years in the Church of Scientology, where he attained those high levels you only hear about in HBO documentaries. But he got out about three years ago and is now a vocal critic of the Church.

He just published a book called Scientology: A to Xenu: An Insider's Guide to What Scientology is All About.

We spoke with Chris about what tipped him off to the Church's deceptions, what he was taught about Xenu, and what he believes would be the single biggest blow to the Church's existence.