It's a journey through a remote part of New Mexico to a place he says few people have ever seen of a super-secret bunker run by the controversial Church of Scientology.
From the air, it looks like a relic from ancient times. Symbols are carved into the mountain. In a video, you can see reporter John Sweeney approaching the entrance which is monitored by surveillance cameras.
Sweeney said at the gate, "Hi, hello, my name is John Sweeney. I was wondering if it would be possible to have a look at the base."
He didn't get past the front gate.
He documents it all in his new book, Church Of Fear: Inside The Weird World Of Scientology.
Sweeney has a long history investigating Scientology. You may remember a memorable confrontation he had with them in 2007. Sweeney lost it while speaking with church spokesman Tommy Davis, who is also the son of actress Anne Archer.
Sweeney told INSIDE EDITION's Paul Boyd, "I made a fool of myself that day."
"What happened that day?" asked Boyd.
"I thought they were trying to brainwash me. I thought I was in danger of losing my mind and I'm afraid to say that I lost my temper," said Sweeney.
And as for that secret bunker, he says he knows what's behind all the security.
"Inside there is a vault. There are three big H bomb-proof doors. Inside those are the lectures of L. Ron Hubbard, the founder of the Church of Scientology, and they are stored in gold.
And those symbols carved into the mountains? He says ex-members told him they were put there so the church's treasures can be located from outer space by aliens.
The church sent this statement to INSIDE EDITION:
"Mr. Sweeney's allegations are silly. The facility is a Church of Scientology archival storage for the preservation of L. Ron Hubbard's scriptural writings and lectures."
And those symbols carved in the mountain? The church's says it's a "corporate logo" to "help pilots find the facility. This is commonly done by major corporations."
Boyd told Sweeney, "The Church of Scientology says these symbols are simply to help aircrafts find their storage facility."
Sweeney said, "I've been to a lot of airports and I have never seen enormous space alien signs. Frankly, that is mumbo jumbo. That's nonsense, it's rubbish."