Sheila Harrison (Anne Leighton) is the main villainess from the Criminal Minds episode, "What Happens in Mecklingburg" (airdate April 9, 2014).
In May of 2007, Sheila's mother, Susan died of ovarian cancer; because she was 18 years old at the time of her mother's death, she was able to obtain custody of her younger sister, Lauryn-Anne.
On February 16, 2013, Lauryn-Anne (who was a student at Mecklingburg State University) attended a party hosted by the Beta Delta Sigma fraternity where she was raped by three fraternity boys: Adam Richmond, Trevor Burkett and Christopher Stafford.
After Lauryn-Anne's rape, she was forced to drink an excessive amount of alcohol and she was dumped in front of her house where she managed to call Sheila, giving her the names of her rapists before losing consciousness. When Sheila got home, she found Lauryn-Anne and took her to the hospital where she slipped into a coma & placed on life support.
During that same night, a fraternity brother, James Linwood had died at the party and Sheila was presumably upset that his death received a lot of attention from the media.
The initial hospital report on Lauryn-Anne documented the results of her rape, but it was changed to "rough, consensual intercourse" by Dr. Edward Calder at the behest of his friend, Michael Smith, who was the football coach at Mecklinburg State University (where Adam Richmond & Trevor Burkett were members of the team). Sheila had managed to see the initial report and was furious at those who were responsible for what happened to her sister.
By 2014, Lauryn-Anne's medical bills had bankrupted Sheila and doctors told her that it was time to shut off Lauryn-Anne's life support.
On April 7, 2014, Sheila abducted Michael Smith, taking him to an abandoned building located near the home where the fraternity party was held. After learning from Coach Smith that Trevor Burkett was one of Lauryn-Anne's rapists, she abducts him as well.
During the abductions, Sheila wore a pig mask to symbolize the Beta Sigma fraternity.
The next day, she abducts a girl named Christy White (who she blames for taking Lauryn-Anne to the party) in a parking lot and tazes Christy's friend, Debbie Martin when she tries to intervene.
Later on, Sheila physically assaults Trevor and proceeds to sodomize him in front of Christy and Coach Smith. She later removes the duct-tape from his mouth and when Trevor apologizes for what he did & pleads with her to let him go, Sheila pours hydrochloric acid down his throat (after tricking him into thinking that it was water), severely burning it. She then releases Trevor into the woods where he is later discovered & rescued by a pair of hunters.
After Sheila gives permission for Lauryn-Anne to be removed from life support, she spies on Adam Richmond and abducts him. When she demands to know what he did to Lauryn-Anne, Adam says that he was drunk & doesn't remember, so Sheila beats him in the leg with a fire poker.
After Adam finally reveals to Sheila about what happened to Lauryn-Anne and apologizes for his actions, Sheila refuses to accept his apology. She then accuses Coach Smith of covering up her sister's rape and kills him by stabbing him in the the neck with a fire poker.
Just as Sheila is about to murder Christy, the BAU storm in and are able to convince her to surrender, telling her that it's not her fault that her sister died. After that, Sheila is arrested for her crimes.