S14, E6: An underage girl disappears after following her older sister to a college party in Manhattan. The SVU detectives mobilize to recover the missing girl but find themselves thwarted by a high-tech kidnapper using the internet to cover his tracks. As the case hits a dead end, DA Barba (guest star Raul Esparza) returns with some unlikely help. Meanwhile, Rollins (Kelli Giddish) is distracted by the sudden appearance of her very troubled sister (guest star Lindsay Pulsipher). Also starring Mariska Hargitay (Detective Olivia Benson), Ice-T (Detective Odafin Tutuola), Dann Florek (Captain Donald Cragen) and Danny Pino (Detective Nick Amaro).