(NBC) — Friday’s “Dateline” is an all-new two-hour episode, involving a family’s relentless pursuit of justice, after the death of Nevada attorney Susan Winters is ruled a suicide.

On Jan. 3, 2015, Winters, 48, was found unconscious in her Henderson, Nevada, home outside Las Vegas. The manner of death was listed as suicide, but her parents didn’t believe their daughter had taken her own life. And they would do anything to prove it.

Correspondent Josh Mankiewicz speaks to Winters’s parents about the seven-year case and their efforts to challenge the criminal justice system.

Here is a preview of Mankiewicz’s report:

It sounded like a suicide attempt. Susan Winters had been in the hospital for most of the morning, husband Brent by her side.

DANNY: He said, “My God, Dan, she drank antifreeze.”

The prognosis was bleak after just a few hours. Susan was taken off life support, the Henderson Police Department was notified. This didn’t look like a complicated case, but that depends on who is doing the looking.

JOSH: Did you believe that Susan could take her own life?

DANNY: No.

AVIS: Never.

An open-and-shut case became a puzzle with a lot of missing pieces.

KATE: There’s a lot of clues in this story, but no easy answers.

A family pushed back against the criminal justice system, and they refused to give up.

CHRIS: All we want to know is the truth.

Watch “Dateline: A Cool Desert Morning” Friday at 9 p.m. on NBC4.

About ‘Dateline’

“Dateline NBC” is the longest-running series in NBC primetime history and is in its 33rd season. Dateline is anchored by Lester Holt and features correspondents Blayne Alexander, Andrea Canning, Josh Mankiewicz, Keith Morrison and Dennis Murphy.

The stories range from compelling mysteries to powerful documentaries and in-depth investigations. When major news breaks, they go to the scene, putting the pieces together to bring the viewer the full picture. And in every story they tell, they help the real people who lived the events share their journeys with the viewer.