(NBC News) – Tonight on “Dateline,” Elizabeth Sullivan, a mother of two, suddenly vanishes in 2014. Nearly two years later, her body is found in the San Diego Bay, but medical examiners say she had only been dead for about a month or two.

Here’s a preview of Keith Morrison’s report:

Liz lived near Norfolk, Virginia. The biggest naval station in the country is in Norfolk, in the whole world, in fact. And somewhere in that big cauldron of romantic possibilities, Liz encountered him, her perfect guy,  Matthew Sullivan. Minnesota kid in the Navy, a knight in shining armor.

So, then it became a love story. Matt seemed to promise permanence, stability. He wasn’t just a handsome face. He was a ticket to something better. Matt was reassigned across the country to San Diego, California. But he just wasn’t ready to say goodbye to the most exciting woman he’d ever met. So, Matt proposed and Liz said yes.

CALANDRA HARRIS: I think they got married so fast because he was having a good time. She was having a good time. It seemed like a perfect match, perfect opportunity.

So, then things were very busy indeed, as they bustled around to get ready for their move out to the big naval base in San Diego. And right in the middle of that preparation, surprise, surprise.

CALANDRA HARRIS: She called me and, excuse my French, she was like, “Holy shit, I think there’s a kid in here.” (LAUGHTER)

Liz was pregnant and a bit overwhelmed.

CALANDRA HARRIS: It was this entire period where we could not say “stroller” ’cause she could not breathe. (LAUGH) You know?

KEITH MORRISON: Couldn’t believe it was actually happening to her?

CALANDRA HARRIS: Couldn’t–

KEITH MORRISON: Terrifying–

CALANDRA HARRIS: –believe it. Couldn’t believe it. She was our permanent rock star. She did not see that coming.

No, she didn’t. A new town to deal with, a new husband, a new baby. But, also some old demons that weren’t done with her just yet.

Friday’s two-hour broadcast features an inside look at the investigation to unravel what really happened to Sullivan, as well as Keith Morrison’s exclusive interview with the person found guilty of killing her. Watch “Dateline: Secrets by the Bay” tonight at 9 p.m. on NBC4.