The darkest and most disturbing case report from the files of Kinsey Millhone, Y is for Yesterday begins in 1979, when four teenage boys from an elite private school sexually assault a fourteen-year-old classmate--and film the attack. Not long after, the tape goes missing and the suspected thief, a fellow classmate, is murdered. In the investigation that follows, one boy turns state's evidence and two of his peers are convicted. But the ringleader escapes without a trace.