10 months prior to the episode's events, Ellen Connell was involved in a two-car collision that killed the other car's passenger, Hannah Miller, and paralyzed the driver, Abby Benson. The accident damaged Ellen's frontal lobe, which prevented her from controlling her fits of rage. Ellen was released from the hospital after six months, and right afterwards, she began committing murders to vent her anger. Her first victims (unseen) were Kevin Brown and Rick Mendoza, and in each case, she killed them in their homes with multiple stab wounds. After each murder, Ellen would pull out strands of her hair as part of a coping mechanism.
In the very beginning of the episode, Ellen killed Jessica Randall at the salon where she worked, and she returned home and washed the blood from the knife. At her workplace, Ellen lashed out at her co-worker, Sarah Ryan, for taking credit for a project that Ellen had worked on, only for Sarah to snap back and state that she covered for Ellen while she was hospitalized. Later on, Ellen invaded Sarah's home and killed her boyfriend, Greg, before chasing Sarah into her bedroom with knife in hand. Ellen forced Sarah to admit to stealing her idea at work before she killed Sarah with a single stab wound.
Ellen's odd behavior was noticed by her teenage daughter Sky, as well as her husband, Michael, who confronted her. It was during the confrontation that Ellen revealed that she had been wearing a wig, when she removed it to reveal her battered scalp, while also revealing her killing spree. Michael intended to call the police, but she was stopped by Sarah, who plunged a knife into her husband, killing him. After killing Michael, the deranged Ellen took Sky and forced her to drive to the home of Abby Benson, who Ellen blamed for ruining her life. Once they arrived at the home, Ellen attacked Abby's mother and went after Abby, while claiming that her lack of attention caused the accident. However, Abby revealed that she actually had the right of way and Ellen caused the accident. Ellen later held Sky at knifepoint after the BAU entered and later advised Ellen to stand down. After Ellen drops the knife, she is arrested and taken away.