The puzzling death of pregnant Ronna Bremer remains a source of anguish for her family, even decades after the discovery of her skull on a Missouri hillside. 

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

“It’s challenging,” she shared with prosecutor Kelly Siegler in a preview for a new episode of Cold Justice, airing Saturday, Sept. 27. “You should never hear such agonizing cries from anyone you love.”

Siegler, alongside homicide detective Terri Hook, collaborates with the Christian County Sheriff’s Office in an episode called “Mountain of Secrets,” aimed at revisiting the intricate case from 1988, the year Bremer vanished. 

The episode description reveals, “The Cold Justice team delves into the enigma surrounding a pregnant mother’s death, whose skull appeared on a forested mountain. With numerous suspects and clashing accounts, will they be able to unveil the truth and secure justice for her and her unborn baby?”

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 duo spent their youth in Iowa, riding bikes to an ice cream shop, and later upgrading to mopeds to explore the rural roads as they grew up. 

“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.

“No parent should ever face that,” Stevens said, holding back tears. “My dad passed away soon after. I believe 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.