SPOILER ALERT: Do need read ahead if you have not watched the “Pretty Little Liars” Season 6B finale, which aired on Tuesday, March 15.

“Pretty Little Liars” creator Marlene King has been teasing a twin for quite some time, and on Tuesday night’s Season 6B finale, that twin was finally revealed. Turns out, Mrs. D (Andrea Parker) has a twin sister named Mary Drake — and she’s come back to haunt Alison (Sasha Pieterse) with some pretty twisted mind games.

In the shocking finale, a fresh-out-of-the-grave Mrs. D lookalike scared the living daylights out of Ali, popping up unexpectedly, causing a fresh-out-of-the-hospital Ali to believe that she’s hallucinating thanks to the painkillers she’s been taking. An added bonus? She also hallucinated Wilden being back from the dead and in her bed. Poor Ali ended up checking herself into a mental institution with Emily’s (Shay Mitchell) help because she was convinced she’s seeing dead people, but she actually wasn’t.

Spencer and Toby discovered an old file in Radley that belonged to Mary Drake (Andrea Parker), who was a patient there 25 years ago and has a child named Charles — yep, that Charles. The child was adopted by Mary’s sister and Ali’s parents, Jessica and Kenneth DiLaurentis. (By the way, the last name Drake should sound familiar: does CeCe Drake ring a bell?)

While Ali was busy checking herself into a mental hospital, her husband Elliot Rollins (Huw Collins) was busy teaming up with none other than Mary Drake. He was pretending to be Wilden, and near the end of the finale, took of his creepy mask and turned to a dark-haired Mary to say, “I would have done anything for Charlotte” to which evil twin Mary replied, “You proved that when you married her cousin.” (Come on, if you watch “PLL,” you knew a perfect loving husband was too good to be true for Ali, right?)

As if twins, hallucinations, masks and horribly betraying husbands weren’t enough, Hanna (Ashley Benson) also found herself in some serious trouble. After sacrificing herself to A-moji (side note: genius name, “PLL” writers), pretending to be the one who killed Charlotte, Hanna’s plan goes awfully awry when Hanna is kidnapped and taken to the bell tower where she is unconsciously being dragged across the floor when the episode ends. Back with the rest of the liars and the boys, a text is received and it’s from a mysterious “A.D.”

In brighter news, the finale was lightened up by bringing some of our favorite couples back together. Spoby teamed up to crack the Mary Drake case at Radley, and Haleb and Ezria teamed up in bed — a flashback revealed that Hanna never truly wanted to leave Caleb (Tyler Blackburn) and tried to run back to him after she left for New York, but he was already in Europe. And Aria (Lucy Hale) and Ezra (Ian Harding) had congratulatory sex, after their book proved to be a hit.

Here, “PLL” creator Marlene King tells Variety what couples may be together in Season 7, and answers all of our burning questions from the finale.

So was that the scariest episode of “Pretty Little Liars” ever? Mary Drake popping up everywhere was terrifying.
Although the cast films it, they don’t see the episodes until they air and the screams and the jumps, I mean, my arm is black and blue from Ashley Benson grabbing me all night so I think it was a success.

How long ago did you plan the storyline with Mrs. D’s twin? Since the beginning?
Not since Season 1, but we started talking about it when Big A, Charlotte, stole the game from Mona and we started wrapping our brains around what the mythology of that character was. Since the Season 5 finale, fans have wanted to hear the end of the Charlotte story, but that’s not complete. I remember telling Andrea Parker that when Mrs. D died that we were going to see her for a long time so it was a few years ago that we really started launching this idea.

And she was just promoted to a series regular, so she’s not going anywhere.
Yes! Which make me very happy.

You’ve always said she is the true villain of the story. Did you say that because it tied into the twin storyline down the road?
You’ll find out more about that, but I will say that still holds to be true in many ways.

When will Ali find out that her mom had a twin? She can’t think she’s hallucinating forever. 
That’s all part of the story moving forward. When we come back this summer, you’re going to find out a lot of answers. Season 7 is really the fastest-moving season we’ve ever had. It moves even quicker than Seasons 1 and 2, and you’re going to get answers almost on an episode-by-episode basis. So you’re going to get that answer really soon.

Is it safe to assume that Ali is in danger in the mental hospital?
Yes, it is safe to assume that! [laughing]

Elliot is not who he seemed to be. What is that backstory — how does he know Charlotte and Mary Drake?
That’s all a part of the mystery moving forward. You will find out in the next few episodes who you can trust, who you can’t trust and why everybody is doing what they’re doing.

Is Elliot even his name?
I can’t tell you that because that’s part of the story moving forward, too.

There was obviously a romance between Elliot and Charlotte. Will we get to see their relationship play out in flashbacks in Season 7?
I hope so. We have a plan for some flashbacks with Vanessa [Ray] who plays Charlotte, and we hope we can get her back on the show because she’s on “Blue Bloods,” but that story will be told and hopefully through flashbacks. There is a rich history there between Charlotte and the character that we know as Elliot Rollins, and we’ll learn a lot more about that in Season 7 and why Rollins is doing what he’s doing.

You said that Season 7 will move really fast. How soon will Alison start to understand that Elliot is not her true loving husband?
I will say that the PLLs are on it a little quicker than Allison is.

Who is A.D?
A.D. is Uber A. The girls early on will realize that this A.D. has uber capabilities and it’s really the scariest “A” of all.

Will that person be revealed in Season 7?
Yes, yes.

Will that reveal come in a big finale ender or will it come sooner in the season?
There will be hints of it within the season. It’s a roadmap, as we say. There are a lot of twists of turns, but I will say that both of the Season 7 finales [midseason and ended] will be even more epic than what we watched last night.

Do we need to be afraid that Hanna is dead?
She appeared to be dead, that’s for sure. You’ll find out the answer to that when we premiere this summer.

Haleb is back! We learned a lot of their backstory last night and clearly they both still love each other. If Hanna makes it out alive, will they be back together?
Haleb, we obviously realized last night that they still have strong emotions for each other and some unfinished business, but it’s by far become our most complicated relationship on the show, now that Hanna has given Spencer the OK to fall for her ex. And Hanna is still engaged so there’s a lot of complexity going on there.

Ezria was back on last night in a really hot-and-heavy scene. Will they actually be back together or was it just a one-time thing?
That scene reminded me of the pilot how those two just cannot deny each other and these moments of high emotion.

Seeing Spoby back together, even if not romantically, got a lot of fans excited — any chance for them to get back together as a couple?
I think the most telling thing about Spoby was how Caleb snapped at her at the end of the episode because he had such strong feelings toward Hanna’s disappearance, and that look that Toby gives is very telling. So that’s what I’ll say.