Law & Order: SVU Season 18 is about a rapist who claims he is genetically preconditioned to rape women.

When a bartender named Jessica is raped, it is at first presumed that an obnoxious guy who was hitting on her is the guilty party, but surveillance footage rules that out. Instead, the detectives find out that a man named Nick Brown was responsible for the rape. Nick confesses but says that he has the "rape gene." Furthermore, he has information about another rapist.

Nick and the other accused rapist, Sam, are in a support group together run by a man who claims that they all have the rape gene and can't help raping women just like alcoholics can't help drinking. The detectives stake out the meeting and arrest a bunch of attendees after one pulls a knife on Nick. Among them is a serial rapist named Sam.

Sam's case is quickly in jeopardy when he claims the group should have been confidential because the leader is allegedly an ordained minister. Barba has to think quickly to salvage this case, and what he does may make things worse rather than better.

To find out what happens, watch Law & Order: SVU Season 18 Episode 13 online.