When 25-year-old schoolteacher Christy Mirack is found brutally murdered in her Lancaster, Pennsylvania, apartment in 1992, there is no shortage of suspects. Frustration and fear mount as each person is ruled out, one by one, and eventually the case goes cold. Twenty-six years later, in 2018, cold case detectives get a break when a relative of the killer uploads DNA to a public genealogy website. This story features a rare interview with the victim's brother and the forensic genealogist who helped crack one of state's first cold cases to be solved by familial DNA technology.