In the 1970s police at Ohio State University arrested a man for a string of campus rapes. When examined by a doctor, it was determined that Billy Milligan had what was called multiple personality disorder. His personas were of different ages, genders, and temperaments. Milligan's case fascinated the public, law enforcement, and medical experts alike.

Join us this week as our host, Rebecca Lavoie sits down with Billy Milligan's sister and veteran teacher, Kathy Preston.

This episode contains spoilers, so make sure to watch all four episodes of “Monsters Inside: The 24 Faces of Billy Milligan” before listening on.