Pretty Little Liars 6x10

Who killed Toby's mother? Who hit Alison in the head with the rock the night she went missing? Who is Red Coat? Who killed Bethany? Who is the Black Widow? Why has "A" been targeting the PLLs all this time? After years of torture, Alison, Aria, Emily, Hanna and Spencer finally come face-to-face with their tormentor and learn the story of how and why Charles became "A."