(NBC News) — Friday on an all-new “Dateline,” firefighters make a grisly discovery while responding to a fire at a suburban house in Toronto, Canada. As a family searches for answers, investigators launch an elaborate undercover sting that reveals a devious murder-for-hire plot and the ultimate betrayal.

Here is a preview of Andrea Canning’s report:

The house on Pebblestone Crescent was still smoldering when police broke the news to Franca: The body found in the garage was her daughter Carmela’s.

FRANCA AGOSTA: I just miss her so much.

Her cause of death was still unknown.

FRANCA AGOSTA: They just said, “It could be an accident. She coulda died in the fire. We don’t know.”

Carmela’s sister Nancy thought about how Carmela sometimes smoked in the garage.

NANCY BURRIDGE: Their dirt bikes are in there, so we’re, like, “Maybe something happened with that– with the gasoline and stuff,” like, who knows, right?

So, an accident, maybe. But when police brought up the possibility of a drug overdose —

ANDREA CANNING: Did you believe that she could do drugs–

FRANCA AGOSTA: No, God, no. She didn’t even drink. She had– an occasional glass of wine.

A few days later, the pathologist told detectives how Carmela died.

DETECTIVE DIANNE JENNINGS: It was confirmed that it was, in fact, a homicide.

She’d been murdered.

Watch Friday’s “Dateline” on NBC4 at 10 p.m.

“Dateline NBC” is the longest-running series in NBC primetime history and is in its 31st season. Dateline is anchored by Lester Holt and features correspondents Andrea Canning, Josh Mankiewicz, Natalie Morales, Keith Morrison and Dennis Murphy.

Dateline is the #1 Friday newsmagazine and reaches more than 17 million people every week through its broadcast, and millions more through its social media platforms and podcasts.

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.