Police were stymied and the crime lab was stumped -- they would need a big break to solve the mystery of the missing wife.

And soon they got one: a chilling piece of evidence found miles away, in a barren stretch of desert.

An unhappy marriage... and an unholy discovery. Dateline Correspondent Keith Morrison reports on "Body of Evidence."

Read a preview from Keith on the Inside Dateline blog, talking about his jailhouse interview with the suspect:

"Even in his drab prison jumpsuit, chained and handcuffed, confined behind a thick glass barrier in the county jail, Sean Goff is an engaging man. Which shouldn't have surprised me, of course. After all, the man was a minister, a youth pastor, before-- well, before what he did.

We met in the narrow confines of the visitor's center, separated by that barrier, not long after his conviction for a crime that was so horrific it had left more than a few people pondering the possibility for evil in one human soul. Did I expect his face to betray something sinister or monstrous?" Click here to read more.