Oliver Goldstick talks with THR about whether Charles DiLaurentis is Jason's twin and why Andrew Campbell isn't who he seems.

[Warning: This story contains spoilers from the season-five finale of ABC Family's Pretty Little Liars.]

There is one name on every Pretty Little Liars fan's mind after Tuesday's game-changing finale: "Charles." But who exactly is he?

The ABC Family drama threw viewers quite a curveball in season five's final episode, revealing that Mona (Janel Parrish) is still alive. She and the Liars have been trapped by "A," who we find out goes by the name of Charles DiLaurentis.

Read more 'Pretty Little Liars' Season 5 Finale: "A" Revealed, New Threat Emerges

Sadly, Charles' face wasn't shown (gah!), but executive producer Oliver Goldstick tells The Hollywood Reporter exactly when this will happen, explaining that Charles is someone who is quite familiar to PLL fans.

Goldstick also discussed the clues regarding Jason DiLaurentis' (Drew Van Acker) possible twin, the show's upcoming time jump and what is next for the girls' love lives (translation: big news for Emison fans!).

What was the thinking behind deciding the Charles reveal?

The thinking behind it is: This is not something that is going to be a total shock to the audience because it's been planted, so we're not just taking something out of left field. So hopefully, this will be something that pays off beautifully for those who have been following us for so many seasons. It's still in a surprising way — I'm not going to say it won't be a surprise! But it won't be like, "Where did this come from?" You'll be like, "Oh, yes. I knew it." And there are probably some people out there who already are ahead of us and go, "Uh-huh, I knew it. Why don't they put me on the Rosewood police force?"

So, just to confirm, Charles DiLaurentis is indeed "A"?

Well, I'm just going to say that anagram is going to lead to the answer. That name will lead to something that will not be a red herring. We look at it as a key that is going to open a big ol' door in six A. And our sixth season, which we're writing right now, the first half of it is very compressed. It really deals with the fallout of that bunker and the four girls having this key now and just finding the right door. The Charles identity — even though it becomes sort of like, "What? Who is this person?" — I think it will all make sense when they find the right door.

See more Broadcast TV's Returning Shows 2015-16

The finale seems to suggest that Charles is Jason's twin.

I'm not going to substantiate that it is his twin, so just so you know that. That's a lovely theory to have, and you might be right, but I can't say if you're right or wrong at this point. I wouldn't go to Vegas and bet on that one — I would hold on to your money. It will pay off for you, but I think you need a few more clues before you can do that. I'd wait until season six, and by the second [or] third episode, you will be able to put your bet down.

But Charles is part of the DiLaurentis family?

Uh, yeah — maybe! Yes and no, I'm going to say yes and no. How about that for facetious? Yes and no!

When do the Liars — and the viewers — ultimately learn A's identity?

They find out a real juicy clue by the first couple episodes of season six A — as I said, it's a three-week time period; we're only doing 10 episodes for the summer — and by episode 10, you will know why the name Charles DiLaurentis came out of that anagram. A's face will be before you — it's a shocker, but A's face will be sprawled across the big screen in episode 10 of six A, the finale. That's a promise.

Is it safe to assume that Charles is someone we've met before? You're not casting a brand-new actor for the role?

No, no. That I can guarantee you. You've definitely met this person.

There's talk about the show planning a time jump. What can we expect with that?

Yes, [when] we start six B, yes. What we're doing is, we're framing the six-A season as three weeks before graduation. They basically come back, and we're making that quick ascent to prom and commencement.

So the show will be skipping past the four years of college?

Well, I don't want to talk too much about that because it's premature, but it will be a lovely jump and really satisfying.

Read more 'Pretty Little Liars' Boss on Season 5 Finale's "Disturbing" Reveal: "It Really Is a Game-Changer"

When season six begins, will the Liars still be stuck in A's dollhouse?

Yes. They've been there for a while, and their wigs are not looking any better — well, at least one wig is not looking good. They're stuck in there for a period of time, and we will basically revisit that period of time through their individual traumas throughout six A. So you will be basically revisiting some of the things you didn't see between seasons through flashbacks.

Seeing Mona return from her presumed death was quite a shock. What was her plan, and what's next for her?

Mona basically had a very specific plan where she could outsmart A, unearth the identity and then expose it to the girls and return to Rosewood as a hero. That was her plan, but guess what? Mona is dealing with someone as smart, if not smarter, than her. I think it's important that you keep in mind that there are three brainiacs in Rosewood: Spencer (Troian Bellisario), Mona and Andrew Campbell (Brandon Jones), and that's a very important thing to keep in mind.

Right. The finale hinted at the fact that Andrew might be up to something. How involved will he be in the storyline moving forward?

Oh, you'll see. It's juicy, and his involvement is deeper than you think — I should say, his connection to what's happened to the girls, what they've been going through, is much deeper than you think.

What is the tone of season six at the start?

It's really a gamut of emotions, quite honestly. We just had a table read for the first episode, and it's not just one thing. It's hard because I want to say "intrigue," but it's more than that, obviously. It's "intensity" — that's the word.

Once the Liars find out who A is, what's going to be the new focus of the show?

With what we've done with these girls for this many seasons, I don't think you can get rid of A that quickly — it's not a rash. This is the fallout of A, and that many years of mental torment, it follows them. It's not going to go away. There will be vestigial impact, even after they know who A is in episode 10. It does not go away quickly — you'll see!

What relationship developments can fans look forward to?

I think there's some really, really nice, soulful relationships happening. There will be some different bonding you haven't seen [that will happen] because of the dollhouse.

Any more romantic sparks between Emily (Shay Mitchell) and Alison (Sasha Pieterse)?

There's romance for both of them — I'm not going to say if it's with each other, but there's romance. Maybe it is with each other, but there's big romance for them coming up in the next season.

Pretty Little Liars' season-six premiere airs in June on ABC Family. Let us know in the comments who you think Charles is!

Email: Ryan.Gajewski@thr.com

Twitter: @_RyanGajewski