Andrew Campbell, whose sketchy behaviour made him the prime suspect in the kidnapping of the Liars, is missing, and Tanner and group are on the lookout for him after they found surveillance equipment in Campbell Farm.
The police think that Andrew has been obsessed with the girls since Alison's disappearance, and the note that Tanner was reading in the premiere episode strongly pointed out that Andrew has motives to hurt the Liars.
Here's what the note read: "It's people like them, people like Aria with her aloof, doe eyes, and Spencer, that smug overachieving ...know it all, and Hanna and Emily that are the root cause of all that is bad in this world. They like games? Well so do I. I fantasize about watching them scream about watching what it takes to make them turn on each other. It's not that I hate them, I don't. They aren't evil. They just play everyone like they're game pieces, like pawns. I'm no pawn, and they can't play me."
And in the next episode, Tanner will succeed in landing Andrew behind bars, as a part of the synopsis of "Songs of Innocence" states that "even with suspected tormentor Andrew in custody, Aria, Emily, Hanna and Spencer fear they are far from safe."
Although all evidence point towards Andrew being Charles, he does not seem to be the main tormentor, as executive producer Marlene King earlier said that Andrew's backstory will be revealed in the first few episodes. However, it will take at least eight more episodes before Charles is unmasked.
She also added that Andrew is connected to the whole drama, and the extent to which Andrew is involved will be revealed in the first couple of episodes of season 6.
"The connections aren't random. He's definitely involved in this, and we will find out in the next couple episodes to what extent and what's going on with Andrew," King told People in March.
"Pretty Little Liars" airs Tuesdays on ABC Family.