When Blake receives a call from her father, a retired detective, informing her of a possible serial killer who has struck again in Kansas City, the BAU investigates the link between the recently murdered triathlete and two high school teenagers who were also beaten and killed a year ago. Scott, Blake's younger brother and a KCPD detective, butts heads with his sister and father as he believes the two cases are unrelated, but it comes to light that each victim had been found wearing only women's underwear. The UnSub strikes again by killing a couple whose daughter Laurie attended the same high school as the two slain teens. The triathlete had also been a substitute teacher at the school. After they discover that a fellow student named Riley died in a possible suicide, Scott questions another former student, Charles, about Riley's death and is attacked by the UnSub lurking in Charles' home.Scott is rushed to the hospital and the team finds Charles dead. After they question Laurie about Riley, she reveals that Riley was bullied by Charles and her boyfriend Lance, recalling a prank in which the boys forced Riley to wear women's underwear in front of the entire school. They identify Riley's friend Ronald as the UnSub who was witness to the prank and vowed to take revenge upon everyone involved, including the substitute teacher and another teacher who intervened. The team tracks down a steroid-addicted Ronald just as he is about to kill the teacher for his futile efforts to stop the bullying. Ronald had targeted the two initial victims as surrogates and then proceeded to hurt or kill everyone involved in the incident. After the case is closed, Blake and Scott finally reconcile their respective family issues.