For all you "Pretty Little Liars" fans out there, the series finale was an intense watch. For all those who haven't seen the last episode yet, I am warning you now this article will have spoilers!

I am still in shock from that episode, and now I want to re-watch the whole series in order to pick up on any clues that I missed, because I would have never guessed that Spencer would have a twin.

The last episode revealed that Spencer has a twin, who was A.D (which stood for Alex Drake) this whole season. She has impersonated Spencer several times within the season and nobody even knew. There were several moments when Spencer wasn't acting herself or wasn't being portrayed the way she usually gets portrayed, and that is because she was actually her twin, Alex. Let that sink in. Twins run in that family I guess.

I was talking to my sister and trying to explain Mary Drake and how Spencer was related to her and Alison.

Mary Drake and Jessica DeLaurentis are twins. Jessica and Mr. Hastings had Jason. Mary Drake impersonated her twin Jessica and got pregnant with Mr. Hastings' twins, Spencer and Alex. Alison's parents had Charles and Allison. Charles ended up being a transgender female (Charlotte) and was sent to Radley where she lived for a while. Mary Drake spent most of her life in Radley as well and that is where she gave birth to Spencer and Alex. That is why when Spencer went to Radley in season 3 she felt "at home".

Charlotte was "A" in season 6 when the girls were locked in the underground bunker which they called a doll house. Once they get back home and Charlotte gets out of jail she ends up dead, which looks like a suicide. That is when Alex took over being "A.D". Alex wanted revenge for her half sister who took care of her when she had no one else. That is where Wren helped her.

After mistaking Alex for Spencer in a bar, she explains everything to Alex. Wren then helps her impersonate Spencer. She was pretending to be Spencer in the cabin during Spencer and Toby's sex scene, and when she asked Toby for a goodbye kiss. She also pretended to be Spencer when Ezra caught her talking to Wren in the airport. All Alex wanted was to be Spencer and when Wren couldn't accept that, she killed him.

It's crazy to me that Jenna picked up on the switch, and the horse noticed but Toby never did. He knew in the end when he chose the right Spencer and handed over Alex to a cop. But was he a cop? Mona never stopped playing the game, but she never figured out who A.D was until the moment Alex got "arrested". The cop who took Alex away also caught Mary Drake and brought them to Mona's own doll house in France. Turns out the "cop" was Mona's boyfriend. Now Mona gets a little revenge of her own.