Pornographic photos from 15 year-old Savannah Biel's house party quickly circulate around her Tribeca high school and go viral. Barba's efforts to arrest the student responsible for posting the images is stalled when several suspects fall victim to a fast-moving measles outbreak. When Benson's foster son also catches the illness, she investigates a group of mothers who may have falsified their children's medical records. Meanwhile, Amaro receives some distressing news about his son.