In this final episode of season 4, Phelps interviews a suspected serial killer, who he believes could be responsible for Dana Stidham’s murder—the first time anyone has spoken to the suspect about the case in 33 years.  After confronting him with the evidence, Phelps implores law enforcement to knock on the suspect’s door and interview him. A final call is made about the connection between the two murders - and who, ultimately, is to blame.