If you're not well-versed in serial killer history (and that's probably a good thing), you may not have immediately known who the mysterious ADT Serviceman was in Mindhunter Season 1. But with some research, fans could pretty easily discover that he was the serial killer known as BTK. The BTK Killer will be in Mindhunter Season 2 even though his face wasn't shown in previews. Again, you need to know a little bit about Dennis Rader — who, per The Washington Post, gave himself the nickname BTK, "Bind, Torture, Kill" — to recognize his appearance. Yet, there was a major sign in the teaser trailer that BTK will return when the new season drops on Aug. 16. Just don't expect that FBI agents Holden Ford and Bill Tench will be the ones to catch him.
During Mindhunter Season 1, a mysterious ADT Serviceman popped up at the beginning of most episodes to engage in suspicious and unsettling behavior in Kansas. While he never murdered anyone onscreen and was completely separate from the investigations Ford and Tench were doing, his presence was foreboding — especially because he was the last character viewers saw when Season 1 ended.
As he burned drawings of bound female bodies, you could assume that BTK would be back and be a major figure in Season 2. The Mindhunter teaser trailer confirmed this when a man wearing lingerie and a female face mask was briefly shown.
Before he was captured and found guilty in 2005 of murdering 10 people from 1974 to 1991, The Wichita Eagle reported how Rader would often strangle and tie up his victims. The Mindhunter Season 2 teaser trailer shows a frightened woman approaching her bathroom where something is tied up. So viewers may have recognized that this could be a crime that Rader committed. But, as Nerdist noted, the preview is even more direct in its reference to Rader since the person in the mask is BTK.
Inverse pointed out that the mask featured in the teaser is the same as the one that was shown in court during Rader's sentencing hearing in 2005. The AP shared an image of the mask and reported how it had been found on the body of Rader's last-known victim, whom he had killed in 1991. After strangling her to death and throwing her body under a bridge, "The defendant returned later to take Polaroid photographs of her wearing the mask Rader himself had worn for his own bondage fantasies, police say," AP reported.
Sonny Valicenti, the actor who portrays the "ADT Serviceman," has also shared on his social media how he's back for Season 2. On Instagram, he shared an image of him in character with a shovel, presumably burying the body of one of his victims. He Valicenti also shared the teaser trailer with the words "oh sh*t," so fans should expect that Rader's crimes will be more explicit in Season 2.
But just because Rader will return doesn't mean that Ford and Tench will catch him. "[The BTK Killer] wasn't caught until 2005. He was literally at large for 30 years! We try to remain true to the details of the crimes ... we may never catch the guy," Tench actor Holt McCallany told Refinery29 after Season 1. "Our journey begins in 1978, are we really going to go up to 2005? I don't think so. We'll span a number of years, but not all of those years. These guys don't solve all of their cases. You don't get to solve them all in real life, and you don't get to solve them all in Mindhunter."
Yet, the person who serves as the inspiration for Jonathan Groff's Ford did eventually interview BTK. Former FBI special agent John E. Douglas, who wrote the book the Netflix series is based on, shared on his website in 2012 an interview he did with Rader via live video. Douglas' website noted he had been asked to assist in the BTK case by the Wichita police in 1980. So while Ford's team wasn't looking into the BTK crimes in Season 1, he may become aware of Rader's actions in Season 2, just like his real-life counterpart.
Yet, even with the FBI's investigation and analysis, Rader will continue to terrorize the people of Kansas as he remains at large for decades to come.