Pretty Little Liars: 6 Juicy Hints About the Finale, Straight From Huw Collins

"I don't think anyone but Marlene really knows the true, true answer to that. And for good reason. I think it's a really interesting one. I mean, who knows? It could be Rollins. It could be Mary. At the minute, they're the top of the suspect list. They have to be. I think that it's going to be really interesting to see who it is, and why, and I think that's obviously going to have a really integral part of seeing this mystery come full circle."