|“||I knew you'd come home.||”|
Bill's wife died after giving birth to their son, whom Bill apparently never named and began to abuse; the boy would later go on to be called Darrin Call. He owned a machine shop and had a criminal record consisting of a few DUIs. In 1973, for reasons unknown, Bill became a serial killer active in Hollow Creek (becoming known as "The Hollow Creek Killer") targeting adolescent boys. He would bring Darrin along when killing and make Darrin help him clean up, dispose the bodies, and other chores. In 1975, one of the victims, Tommy Phillips, escaped with Darrin's help. He tried to take Darrin with him, but Bill caught up to the latter. Darrin defended himself by slashing him in the face, giving him enough time to flee. Bill never went looking for his son, who never told anyone about what his father had done, so Bill got away with his crimes. After that, he apparently stopped killing and lived a regular life, continuing to live in the same household because he could watch the children play across the street. His machine shop was soon closed down in 1980.
Darrin, who has become psychotic as a result of his upbringing, has a breakdown and eventually traces his father, confronting him with his past. The BAU and local police are present, having chased Darrin since he attacked a number of people in a killing spree. Hotch goes inside, tries to reason with Darrin, and then confronts Bill about the murders, and he (not unexpectedly) denies everything. Bill is then killed when Darrin shoots him three times in the chest with a pistol stolen from one of his victims, freeing Darrin from the haunting memories of Bill and his upbringing.
The Hollow Creek Killer was profiled as a patient killer, one who had a lot of free time in the afternoons, when he took his victims, always boys who were leaving a school (one of which he likely lived or worked near). Due to the fact that he tortured his victims over a long period of time, he had to have some secondary, secluded location where he held them captive and abused them. Since Darrin was never reported missing or dead, the killer's wife, who would have wanted some kind of investigation or funeral, had likely died some time before the murders started.According to Hotch, Bill never bothered moving because his house was right across the street from a school; he could spend all day sitting on his porch watching the children, feeling compelled to do so. He also had Darrin sit in the front of his truck to put his victims at ease, and targeted adolescent boys because torturing and killing younger ones would be "wrong". Also, as Hotch put it, possibly as just a taunt, torturing and killing the boys made him feel strong, and like a real man. However, it isn't actually revealed why he killed the boys.
Targeting adolescent boys, Bill would abduct them on their way home from school, having Darrin in the car to make himself appear safe, held them captive in a cage for weeks, and tortured them using a knife, either by stabbing or cutting them with it. He eventually killed them through unspecified means, butchered their bodies, and buried their remains. It is briefly mentioned that he used lime to dispose the remains. He also had Darrin burn their clothes in a metal drum. According to Darrin's flashbacks, Bill (on at least one occasion) kept two boys captive simultaneously, possibly keeping even more.
Bill was possibly based on Gordon Northcott, the perpetrator of the so-called Wineville Chicken Coop Murders. Occasionally using his young nephew, whom he was heavily abusive towards, to help capture young boys, Northcott would hold the children captive for some time, all the while torturing and sexually abusing them, before dismembering them and burying the bodies, using lime on them like Bill.
- 1969-1975: Darrin Call (his son; abused)
- 1973-1975: At least three unnamed victims
- 1975: Tommy Phillips (held captive, tortured for two weeks and intended to kill; he escaped)
- Bill's nickname is a possible reference to both the Hollow Man and the Mill Creek Killer, who appeared in "The Last Word", a Season Two episode which Erica Messer, the writer of "Haunted", co-wrote.