"Charles is the twin of Jason, as we know. So he grew up and was so crazy and obsessed with Alison hence the confusion of two girls and why the mom got him a dress. Kept him hidden in the barn where he met Andrew and they became friends. Prob at one point made his way to radley where he went by the name ali and prob wore a wig. then years later got out and tried to kill the golden child, Ali, not realizing he killed Bethany instead. From there he killed his mother for keeping him locked up and away from Alison. While also drugging Jason and coming in and out as him. And that way he could still do bad things for Jason yet sneak around. He attacks the girls cus they're keeping him away from his sister. Hence also why Spencer's sister would help him him cus that's her brother. He also prob was involved in Toby's moms death."