The mysterious death of pregnant mom Ronna Bremer continues to haunt her family decades after the 22-year-old’s skull was found on a Missouri mountainside. 

Bremer’s sister Deanna Stevens still remembers the moment her late parents learned of the heart-breaking death.

“It’s hard,” she told prosecutor Kelly Siegler in a preview for an all-new episode of Cold Justice, airing Saturday, Sept. 27. “You should never hear those kind of guttural sounds come out of anyone you love.”

Siegler and homicide detective Terri Hook join forces with the Christian County Sheriff’s Office in the episode, titled “Mountain of Secrets,” to re-examine the complicated case dating back to 1988 when Bremer first disappeared. 

“The Cold Justice team investigates the mysterious death of a pregnant mother whose skull was found on a wooded mountain,” an episode description reads. “With multiple suspects and conflicting stories, can they uncover the truth and get justice for her and her unborn child?”

One of their first stops during the renewed investigation is Stevens’ home, where they hoped to get a better picture of the woman Bremer was. 

“My sister was a lovely person,” she remembered. “She was just sweet and sassy and we had a great childhood.”

The pair spent their early years in Iowa riding bikes to the ice cream shop, eventually graduating to mopeds to explore the country roads together as they got older. 

“She was just very carefree and fun,” Stevens said in the preview. “It’s unfortunate that someone so evil snuffed that out of her.” 

The unsolved cold case had a deep impact on Bremer’s parents, who never fully recovered from the loss of their child.

“I mean, no parent should ever go through that,” Stevens said as she fought back tears. “My dad died, you know, shortly thereafter. I think it just…broke him.”

To find out what Siegler and her team are able to uncover about the unusual death, watch Cold Justice Saturday, Sept. 27, at 8 p.m. ET/PT on Oxygen.