(NBC News) — Friday on “Dateline,” when New Jersey mother Michelle Lodzinski reports that her five-year-old son Timmy vanished from a carnival, detectives embark on a decades-long investigation, until a family member identifies a key piece of evidence pointing to a potential suspect.

Here is a preview of Andrea Canning’s report:

It was a moment that devastated nearly everyone in this quiet corner of suburbia.

ANDREA CANNING: This is really a parent’s worst nightmare.

SIBILE MARCELLUS: Yes, absolutely.

The little boy at a carnival — who suddenly vanished.

JIM RYAN: The innocence that we had as a community was changed from that day on.

Everyone was touched by this case, from the parents who swore never to lose sight of their children again.

KEITH HACKETT: I went home, I hugged my kids. I felt so bad.

To the tireless detectives who searched and labored, losing hope they would ever find answers.

MARY ROBILLARD: I have nightmares every May 25 when he disappeared.

Thirty years of twists and turns.

SIBILE MARCELLUS: It’s like mystery on top of mystery on top of mystery.

And then, just a few months ago, the case suddenly came to a dramatic and controversial end.

SIBILE MARCELLUS: That we didn’t see coming.

LINDA HISEY: I screamed. (EMOTION) And I got on my knees.

ANDREA CANNING: This is one of the most shocking twists — for the end of a case that I’ve ever seen.

KEVIN SKOLNIK: Yes. Unbelievable.

Watch “Dateline: The Blue Blanket Mystery” Friday at 9 p.m. on NBC4.