(NBC News) — On Friday’s “Dateline,” when a pharmacist is found shot to death in his Wisconsin farmhouse, investigators embark on a 15-year hunt for his elusive killer.

Here is a preview of Andrea Canning’s report:

Dill Creek Farm belonged to 58-year-old Ken Juedes — a local pharmacist. Married to his second wife, Cindy. She was the woman who’d called 911 and was now holed up at her neighbor’s house.

Detective Sean McCarthy headed to the scene where he met up with his partner, Greg Bean.

GREG BEAN: And on the bed was the victim. He was laying unclothed– with– some major injuries to his chest.

ANDREA CANNING: Bullet wounds–

GREG BEAN: Bullet wounds.

ANDREA CANNING: To the chest.

Ken had been shot twice at close range. And there was something else that caught the detectives’ eye.

SEAN MCCARTHY: On the other side of the bed, there w– was a knife stickin’ through a pillow. It had a white note on it. And– on the note was written the word “bitch.”

ANDREA CANNING: Wow. That’s something you see in the movies.

SEAN MCCARTHY: It definitely got our attention. Like, we hadn’t seen that before.

ANDREA CANNING: That sounds like a revenge thing.

SEAN MCCARTHY: And then you wonder what’s goin’ on here and what was really meant to happen that night, right?

The detectives wondered whether the note was a message not for Ken — but for his wife.

Watch “Dateline” Friday at 9 p.m. on NBC4.

“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.