Spoilers below for the series finale of Pretty Little Liars. Proceed at your own risk. You’ve been warned!
“It’s a lot to process. Would you like a sedative?”
In the end, Pretty Little Liars went out with a massive bang. Confirming a popular fan theory that gained traction during the Freeform drama’s final season, it was revealed in the series finale that Spencer Hastings indeed has an evil, psychopathic British twin named Alex Drake. Let that sink in for a second: Evil. British. Twin.
Let’s unpack how we got here.
A year after the events of the penultimate episode, Mona returns to civilian life after her stint at Welby State by shacking up with Hanna and Caleb for a few nights. Still unaware of who “A.D.” is, she obsessively continues to play the game in the hopes of uncovering the unknown genius’s true identity, and gets a directive to knock Spencer unconscious. She does, and Spencer wakes up in an underground lair — which we later find out is actually the house Toby built and sold, to add insult to injury! — coming face to face with her twin for the first time.
Unbelievable stories have unbelievable beginnings, and Alex’s made-for-TV tale begins when she has a chance encounter with problematic PLL favorite Wren at a pub in London, where Alex works as a bartender. Wren, obviously, thinks she’s Spencer. “I’ve never felt so close to someone so fast,” she explains. “And he felt the same way.” They fall in love and exchange stories about who she really is, and she soon realizes how Spencer got a better life across the pond with a caring family, devoted friends, and never-ending opportunities, while she ended up being abandoned by her rich, adoptive British parents once she started to lash out as a preteen.
Alex becomes fascinated to the point of obsession about what her life in Rosewood could’ve been, and after forging a close connection with her half-sister Charlotte, thanks to Wren, she uses Charlotte’s death to birth the “A.D” persona and avenge her death by torturing the Liars until they reveal who killed her. “Those bitches took her away from me, and now they’re getting everything that they deserve,” she tells Wren in the airport flashback. “I’m honoring her, don’t you get that?” Not really, but okay!
While hatching the scheme, Alex was actually in Rosewood and inhabited the persona of Spencer during many scenes that fans previously dissected as potentially involving her twin — including when she and Wren spoke to Ezra at the airport and when Spencer appeared to Hanna in a “dream” when she was held hostage in a shed. When Mona was revealed to be Charlotte’s killer, Alex decided to go back to London, but her jealousy continued to manifest itself into pain and anger. “I just couldn’t stop thinking about you. How good you have it,” she tells Spencer. “About how much your friends love you. It was just driving me mad.” She wanted Spencer’s life, and she wanted it for good.
Knowing Aria’s Rosewood wedding would force all of the Liars to be at the same place together, Alex comes back to town for one last grand scheme: to actually inhabit Spencer’s life once and for all after she kidnaps her and forces her to live underground. Oh, and Wren didn’t like the plan, but he couldn’t do anything about it because Alex killed him and turned him into a diamond necklace. R.I.P., Wren.
As you probably assumed, Alex’s plan doesn’t come to fruition, as Jenna of all people deduces by smell (by smell!) that Twincer isn’t the real Spencer upon a streetside meeting. She calls Toby, who alerts the Liars, who are already reeling from the fact that Ezra never showed up to his and Aria’s wedding. (Did we not mention that she also kidnapped Ezra and helped Mary Drake escape from prison? That girl has her hands full!) A showdown at the underground lair ensues, with the tense stand-off resulting in Alex getting turned over to the police. However, Mona gets the last laugh — thank god — as a closing scene reveals she’s holding Alex and Mary in her very own glamorous underground lair below a doll shop in France.
“She can’t keep us here forever,” Mary says worriedly.
“Of course she can,” Alex responds matter-of-factly. “She’s Mona.”