The 17th episode revisits the murder case of Mary Davis from North Carolina. Mary was killed in 1987, but no viable suspect was found at the time of the initial investigation. Years later the DNA data from the crime scene had been entered into CODIS, but even that provided no answer. In 2020, new generation of detectives were assigned to the case with the help of forensic investigative genetic genealogy. 

Experts hope forensic science can solve the murder of Melissa Lee, which baffles Washington detectives.