If you watched the first two seasons of 'Mindhunter', odds are you've always wondered why some of the episodes kept darting back to a guy in glasses and a moustache as he went about his business.
There was no reference to the guy in any of the episodes beyond these little diversions, and neither of the three main characters - that's FBI agents Holden Ford and Bill Tench, and Dr. Wendy Carr - ever touched upon his case either. Long story short, the serial killer wasn't invented for the show, but was a real-life serial killer named Dennis Rader, also known as the BTK Killer.
In an interview with Variety, Fincher followed up on his comments about the show's ending, but seemed more hopeful this time around. "At some point I’d love to revisit it,” Fincher told Variety. "The hope was to get all the way up to the late 90’s, early 2000’s, hopefully get all the way up to people knocking on the door at Dennis Rader’s house."
Rader was eventually captured in 2005, after killing ten people between 1974 and 1991, during which time he sent taunting letters to police and newspapers about details of his murders. The BTK Killer was huge news throughout the '80s, with Thomas Harris basing the character of Francis Dolarhyde from 'Red Dragon' on the-then unidentified Rader.
Fincher, meanwhile, said that the work on the second season of 'Mindhunter' was that extensive that there was very little left over to take Season 3 up and run with, adding that he "needed some time away" from it. Prior to this, Fincher said that he didn't think the show could continue given the viewership versus the budget.
Netflix, of course, never releases viewing information and production budgets are normally rough estimates. On the plus side, Netflix hasn't yet given any kind of official confirmation to whether or not 'Mindhunter' is over, as this all seems to be coming from Fincher himself. Given that there was a two-year gap between the first and second season, it's plausible that you might see another gap between a second and third season, or possibly more.
Either way, 'Mindhunter' was far too good of a show for Netflix to lapse.