In the world of "Mindhunter," the Btk Killer is still free. Dennis Rader, the man whose presence and crimes lurked around the edges of the show's two-season run, wasn't caught until 2005, and the second season of "Mindhunter" ended with a grim reminder of his continued serial murders. You can't really blame David Fincher for leaving his historical crime series open-ended; the show based on the book of the same name by John E. Douglas and Mark Olshaker is acclaimed by critics and audiences alike and has frequently been cited as one of the best Netflix originals ever made. It's also pretty darn close to flawless -- creepy and emotional, rich both visually and thematically, and home to some of the most fine-tuned TV performances in recent memory. So why the hell did it never come back for a third season?

The narrative surrounding the end of "Mindhunter" has (like the...