The series "Pretty Little Liars: Original Sin" is a spin-off of the original story about five high school girls investigating the disappearance of their friend. The events unfold in the town of Millwood 20 years after the main plot. The focus is on a completely new set of characters - five teenagers from the same school. These girls are so different that they would hardly be friends... if it weren't for a shared secret. They are all pursued by a mysterious stranger who threatens to reveal something terrifying about their past to everyone.