Elaine Frye Cavanaugh (Lisa Banes) is the true main villainess from "Totem," episode 12.20 of Law & Order: SVU (airdate March 30, 2011). She is the mother of half-siblings June Frye (a piano teacher) and Katie Cavanaugh.
Elaine was believed to have been deceased, as June stated that her mother had died while claiming that her late father molested her as a child. During the investigation regarding the rape and death of one of June's students, Marnie Foster, it was revealed that not only was Elaine alive, but she was the one who molested June. Elaine was strict and abusive to June during her childhood; it was shown during her encounter with Benson and Stabler, as Elaine voiced her displeasure over her first husband (June's father) "spoiling" her (in Elaine's mind). It was indicated that Elaine used a wooden spoon to molest June, and as revealed later on, the evil Elaine also abused and raped her other daughter, Katie, as well.
Elaine's abuse traumatized both daughters, with June claiming that her mother was deceased, while Katie's trauma led her to rape and murder Marnie. When Benson and Stabler chased Katie into her bedroom, Elaine screamed at them to get out of her bedroom, after Katie claimed that it was hers--giving the indication that mother and daughter shared the same room and Elaine's abuse was ongoing. At episode's end, during Katie's confession, Benson informed June that Elaine will be arrested for the abuse, as well as for first-degree reckless endangerment in Marnie's death.