Episode 4 is the fourth episode in the Mindhunter series. It premiered on October 13, 2017.
Bill and Holden consult with Dr. Wendy Carr to begin classifying their subjects. They receive surprising news.
Bill and Holden go to visit another inmate who talks to them about the woman he raped. Afterwards, they are in a car accident. They both are okay but Bill is pissed. The two head to a bar where Holden tells Bill that Debbie can pick them up in the morning. Bill is upset because he didn't see the car coming.
Bill and Holden share their recordings from the inmate with Wendy who has now joined them at Quantico where they analyze the tape. They return to the prison to talk to the inmate again who tells them more about his past. He tells them about how his childhood and how his mother didn't want him there. They conclude that the inmate sees himself as the victim.
They continue traveling around the US teaching other cops. They are approached by another cop with another case. Bill and Holden look at the pictures and realize that they have another killer on their hands. Bill chastizes Holden over making the cop feel less superior because he doesn't know how to analyze a crime scene by their means. They bring the case back to cops and describe what to look for. Together they go back to the crime scene where they learn more about the victim. They meet a suspect but Bill says that he's too old but Holden insists they talk with the wife. The wife says that the girl almost became their babysitter. The wife confirms the alibi so they're back to ground zero.
Wendy chastises them about helping out the local cop saying that they don't have time. Bill is sure that they can do both. Wendy tells them that she's been trying to create a taxonomy for their project. They help her decide on a few words. Holden and Debbie have a talk about marriage while waiting for Wendy to meet them at a local Chinese restaurant.
The next day they are called into the bosses office. They are informed that they were awarded money to help fund their operation. He also tells them that Congress has taken a big interest in them.