S6, E15: Boy scouts on a stargazing mission check out a rooftop and see a dead body. The victim's purse was dumped in the alley and her identification says Allison Downey (Jessica Dunphy). When Benson (Mariska Hargitay) and Stabler (Christopher Meloni) visit Allison's grief stricken mother, her daughter walks in the door. Allison is safe, but her 15-year-old cousin, who used her I.D., is not. Lisa (Janae Kram) was killed by a blow to the head, and was dressed in a very expensive cocktail dress. Upon checking her out, Lisa appeared to be a normal, all-American teenage girl from Queens. But the cops discover a secret life. Her father is a truck driver and not home very much, and her mother just passed away. So Lisa hooks up online with lots of boys, and her liaisons have escalated to prostitution. She also tested positive for HIV.