Law & Order: Criminal Intent S09E07 - Love Sick

Rachel, a young girl from the midwest who moved to NYC, is murdered after visiting a medical center to receive treatment for an assault. Maya, a nurse's aid from the medical center and her boyfriend Damon, engage in a series of sexual assaults and murders. They are responsible for Rachel's death among others. Nichols and Stevens must figure out if Randall, another nurse's aid or Maya and Damon are the killers before there is another murder. The crux of the investigation lies in uncovering the psyches of Maya and Randall as individuals and as a couple.