This Friday, Sept. 18: Dateline's two-hour season premiere!

What mysteries lie at the heart of a marriage? Dateline goes "Behind Closed Doors."

First, a husband and wife who were the very picture of a perfect modern marriage. She was the breadwinner. He took care of the children. And it worked fine, but then there were rumors of an affair, fights over the kids, and finally... an ugly divorce. The marriage was ending, but a crime even seasoned detectives would find hard to believe was just about to begin. NBC's Keith Morrison reports on a case of "Bad Chemistry."

Then: A case that was controversial, and a verdict that was even more so. It centered on a young couple who'd just recently been married. They were settling into a new house and a new life together until something unsettling happened upstairs. The young husband discovered his wife had drowned in the bathtub! It seemed a horrible accident, but police were bothered by one thing: Why was her body dry? NBC's Dennis Murphy reports on "The Mystery in the Master Bedroom."

Join us for "Behind Closed Doors," Dateline's two-hour season premiere, this Friday at 8 p.m. ET, 7 p.m. CT on NBC.