Law & Order: SVU Season 17 Episode 17 centers around an investigation of Catholic school girls who are being used as prostitutes. At first, it seems like an ordinary case. Sonny is undercover at a party where underage girls are being sexed by older men, but when the scene turns violent, it's discovered that some of the other partygoers are also undercover cops, while others are high ranking police and government officials.

Vice claims that SVU ruined its investigation and should back off, but there's no evidence that there really was an undercover investigation, and one of the undercover agents turns out to be a nun, Sister Nina. Sister Nina claims her mission is to help these girls but she won't talk about who is running the parties. She says that "they" will come after her if she talks.

The investigation leads the cops to a girl named Kara, who will only talk in Sister Nina's presence. Kara is soon found dead. Meanwhile, the girls all turn out to go to a Catholic school where Tucker's cousin Eugene works as a guidance counselor. After Kara's death, Tucker accuses Eugene of having a hand in it and the two men almost come to blows. Eugene also tells the detectives that Nina is mentally unstable and should not be around children.

Nina freaks out when Tucker visits her at Olivia's apartment and doesn't seem to want to put Olivia's son down, but eventually she does. Nina then accuses Olivia of trying to have her killed and runs away.

Olivia and Mike go to Barba, who is not surprised. He privately tells Benson some surprising news about Tucker.

To find out what happens during the shocking end of the episode, watch Law & Order: SVU Season 17 Episode 17 online.