For a mother of four who attended a Halloween party in 2011, the real horror began after she left the event.

Karen Swift mysteriously disappeared in the early morning hours of October 30, 2011, after returning home from partying at a country club in Dyersburg, Tennessee. A frightening case that is being investigated in a completely new case Dateline Airing Friday, November 1st at 9:00 p.m NBC.

RELATED: Murder of Georgia woman reveals years-long mystery surrounding two friends who were also killed: 'He was a monster'

“A “Very strange missing person case”

Karen's husband, David Swift, “stayed up late to make sure they got home safely, but when he woke up the next morning, Karen was gone.” Morrison says in a voiceover.

It sparked a years-long search for answers.

RELATED: 'Living in a nightmare': Karen Read speaks out about being accused of killing her Boston cop boyfriend

“It was a very strange missing person case,” said reporter Janice Broach Dateline.

As Morrison said in the preview clip, “The mystery of what happened to Karen Swift became greater than anything this city had ever seen.”

A shocking discovery

According to a report, Karen's body was discovered in a cemetery about two miles from her home about six weeks after her disappearance NBC News reportBut the grim discovery wasn't enough for investigators to piece together the reasons behind her disappearance.

For years, the community wondered what happened to the missing mother in her final moments. The investigation soon stalled until authorities got an unexpected break in the case.

RELATED: 'Dangerous romance' revealed after Texas teen's mother murdered in shocking case with 'many twists'

“Nearly a decade later, a private investigator claims to have uncovered frightening new clues that are turning the city upside down,” the book’s synopsis reads “After the Halloween Party” Consequence.

Private investigator Heather Cohen recounted Dateline that she “came in and I stirred up the hornet’s nest” and revealed dark secrets that had been hidden for years.

In addition to interviews with Cohen, Broach and Ashley Swift, the episode also features comments from attorney Jason Creasy and Terry McCreight, an investigator with the Dyer County Sheriff's Office.

To learn more about what happened to Karen after the Halloween party, regard Dateline on Friday, November 1st at 9/8 p.m NBC or stream the episode on Peacock as soon as it becomes available the next day.

RELATED: 'Sinister conspiracy' uncovered after two people killed and high-speed police chase in Southern California

And for even more Datelinesign up for the show official newsletter and look at it Podcast.

The news magazine is now in its 33rd season and is the longest-running series in NBC Primetime story.