Sorenson, Sipowicz and Medavoy with help from John Irvin, investigate the disappearance of a gay man (with evidence of foul play), whose nephew indicates that his uncle's former lover might be their man. The lover is brought in for questioning, but their questioning reveals that the lover's new roommate might be someone worth questioning as he's referred to the victim as "Satan incarnate." Meanwhile, Russell, Kirkendall and Jones help the meek victim of a gang rape. The victim at least had the presence of mind to keep track of where the gang took her to be raped, despite the fact they wouldn't let her see where they were taking her. Retracing her steps leads the detectives to the apartment where the raped occurred and to "the fifth man in," which will eventually lead them to the other four.