Shannon Coyle, a sixteen year old student, is found dead in an alley. Benson tells the victims mother that she had sex before she died. Benson and Stabler interview the students at her school and everyone seems to be clean except the choir teacher. They go to his apartment and find him having sex with one of his students (Lisa) who happens to be Shannon's best friend. She tells Benson that Shannon was sleeping with a classmate named Aidan.