Up next, a married man falls victim to temptation.

He had made a mistake, which I'm sure a lot of people can identify with.

She offered him a wild side that he hadn't experienced.

Then he vanishes without a trace.

He was there one minute and then gone to next.

For almost 20 years, the disappearance goes unsolved. I kept that hope that maybe he would show up on my doorstep.

Until a tiny chip of paint tells of a terrifying ordeal.

It would drive me crazy to know what a murder victim goes through every time they're killed.

The Kennecott Copper Mine outside Salt Lake City, Utah, is known as the richest hole on earth, and copper isn't the only valuable mineral.

They mine gold and silver, and they have very expensive equipment, that sort of thing,

that theft is a big problem out there.

As a result, security is very tight.

You just don't go onto Kennecott Copper property without usually encountering security.

So when the security guard wasn't on duty

in the guard shack on a winter night in 1991,

it was unusual.

They went up and figured that he might be in the restroom,

checked it out for a while.

They went up and found his lunch was partly eaten.

His hard hat was still there.

The guard, Brian Roof, was not supposed

to leave the shack for any reason

...