The reveal that many fans had spent seasons of Pretty Little Liars waiting for totally blew our minds — and no, it had nothing to do with unmasking A. In the Season 6 finale, we learned that all of those hints really did mean something, and that Jessica DiLaurentis had an identical twin, Mary Drake. However, that's not the only reason why Mary is important — she's also the biological mother of Charlotte and up to something. Is Mary a friend or foe? Is she pretending to help Alison, or does she have a hidden agenda? Right now it's up in the air, but one big clue from the books the show is based on hint that Mary might really be Jessica on Pretty Little Liars, at least, some of the time.
Mary and Jessica may have been sisters, but their relationship was anything but loving, according to Mary. The new owner of the Lost Woods Resort hardly had the nicest things to say about her twin, whom she basically described as straight-up evil. During a conversation with Spencer, Mary claimed that it was Jessica who got Mary committed to Radley in the first place. According to Mary, Jessica asked her to help her calm down a crying child she was babysitting for, whom Jessica said was sleeping. However, sometime during Jessica's babysitting the child had died, and Mary was left responsible for his death. It's a dark story, and one that would give Mary plenty of motive to get revenge on her identical twin. Could she have done that by switching places with her?
In the Pretty Little Liars book series by Sara Shepard, a very similar twist happens. In the books, Alison has an identical twin sister named Courtney, and it's actually Alison who is the evil twin. Alison manipulates her family into believing that Courtney is dangerous and eventually has Courtney committed to a mental institution because of it. One thing that Alison manipulates Courtney into doing is pretending to be Alison in front of their parents, so that it ruins Courtney's credibility and makes her look unstable. However, this ultimately works against her, as Courtney is able to trick her parents into sending Alison back to the mental hospital in her place. When Alison protests that she's not Courtney, it looks like Courtney is trying to manipulate the situation, and the real Courtney poses as Alison for a full year before Alison comes back and murders her out of revenge.
Could a similar situation have happened on the Freeform series with Mary and Jessica? It certainly sounds possible, given Mary's hellish relationship with her sister, but the timeline of the show doesn't quite work out for Jessica to take Mary's place in Radley and still be Charlotte's biological mother. However, a switch could still have happened in other ways — by Mary assuming Jessica's identity to do seriously messed up stuff.
We know that Jessica supposedly had an affair with Bethany Young's father, but that never quite added up. It would have made a lot more sense if it was Mary who had the affair with Mr. Young, so she could ruin Jessica's family the way Jessica ruined her life. Perhaps she did the same thing with Spencer's father, Peter Hastings — it would explain the bizarre conversation that Mary had with Spencer about knowing her parents intimately, but also somehow secretly.
Right now, PLL really wants us to sympathize with Mary's story, but I don't think she's as innocent as she would have us believe. Anyone connected to the DiLaurentis family seems to have a bit of liar in them, and she may have been pretending to be Jessica for quite some time.
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