Stephanie Carter was an outstanding student but was constantly bullied. When she got into high school, she fought back and got expelled for it. After her expulsion, she was heavily medicated but this caused her to further spiral apart. Five years ago, she decided to go off her medications, got a college degree, and married Patrick Carter whom she later became his partner in killing.
Sick and Evil
At the beginning of the episode, she is seen picking a locked door of a woman named Kim Reynolds and then proceeds to stab her to death. The BAU are being called into the scene when they are alerted that the unsub has escalated and kills a couple, the Davis's, by ambushing the husband, Brad, in the hallway and killing the wife, Carly, when she is sleeping. Stephanie later enters the home of Natasha Thompson and lures Natasha into the bathroom by turning on the bathtub faucet. The BAU are alerted to the murder by a 9-1-1 call where they find Courtney covered in Natasha's blood. The woman's daughter, Michelle, survives and gives Stephanie's description to a sketch artist and with the help of Courtney's list of "ghost hunters" and/or people obsessed with the haunted folklore. The BAU realizes she is the unsub and they rush to first her workplace, but she is not seen. It is revealed that she left with Courtney after finding out about a "haunted house" to get "instructions" from her husband, Patrick, on what to do next. The BAU confiscated all her journals and books and found out from one entry where Stephanie and Patrick might be. Stephanie is later revealed to have killed her husband and seems to have been killing under orders from a hallucination of Patrick. Courtney enters the room and find Patrick's body. Stephanie tries to kill Courtney to eliminate any witnesses but Courtney fights back. She falls into her delusions when she overpowered Courtney and attempted to kill her, but Rossi comes into the room and shoots Stephanie dead and saves Courtney.
Stephanie targeted people living in homes that were allegedly haunted. She initially targeted single women but later moved on to also murder couples. She would enter the house by simply entering through an unlocked door as Maine is rural and people don't usually lock their doors or pick the locks with her knife. She would then subdue her male victims by blitz attacking them and subdue her female victims by applying blunt force trauma to them. She would tie her female victims up to their beds and she would proceed to stab them 22 times, killing them. She would also burn sage and place salt in the four corners of the room the victims were killed.
The unsub is female, probably local, and has extensive knowledge of the city's lore. She is obsessed with haunted folklore which makes her very dangerous. This unsub is mission-driven and likely delusional. This delusion may stem from the fact that she thinks the houses are haunted and that the residents are infected by evil. To her, the only way to kill the demon and save the people is by stabbing them 22 times in the stomach. And at this point, it's still unclear why she values the number 22.
- Unspecified date: An unspecified incident of fighting involving bullies
- Unspecified date in January: Patrick Carter (her husband; possibly killed prior to Linda Stahl)
- January 25: Linda Stahl
- January 30: Kim Reynolds
- January 30-31: The attack on the Davis house
- Brad and Carly Davis
- January 31: Natasha Thompson
- February 1: Courtney Mably (abducted, beaten, tied up, and attempted to kill; was rescued)