Steven Gordon and Franc Cano could still be out on the hunt if it wasn't for one determined investigator, Detective Julissa Trapp.

The night of Dec 13, 2001 would forever change the lives of two Early, Iowa families. 

Its been more than 15 years since Teresa Halbach disappeared on a photography assignment for Auto Trader Magazine, but some still question the convictions of the two men found responsible for her murder. 

Denita Smith believed she had met her "perfect" man, but he was hiding a secret that would cost her life. 

Two intruders stormed into the Douglass house in October 1979, robbing the family and chillingly shooting all four as they lay face down on their living room floor.

Dateline reporter Dennis Murphy described the mastermind of the gruesome plot to kill young parents Josh Niles and Amber Washburn as "perhaps the most villainous killer" he's ever come across. 

Lissa Yellow Bird spent years tracking down missing Indigenous women, until one day her own niece Carla Yellow Bird disappeared, sparking a very personal mission to bring her back home. 

Amy Mihaljevic had agreed to meet a man she believed worked with her mom to buy her a special present when she disappeared in October of 1989. Detectives are hoping someone has the key to solving the mysterious case.

Dateline: Unforgettable's Keith Morrison described the terrifying mystery as “unlike anything I’d ever seen." 

Kathleen Peterson was found at the bottom of the staircase in her lavish North Carolina home in 2001, but the mystery around her death continues to endure.