Pretty Little Liars Star "Finds Out" Who Is Texting Secrets

Pretty Little Liars star Troian Bellisario says Tuesday's finale will finally reveal who "A" is -- the mysterious person who threatens to release a group of girls' darkest secrets.

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"One of the pretty little liars finds out," teases 24-year-old Bellisario, who plays Spencer. "We can't tell you when or how or whom that happens to, but it's pretty exciting."

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The Pretty Little Liars are a clique of four popular high school girls who break up their friendship after their fifth member, Allison, is found dead. They suddenly begin receiving mysterious text messages from somebody who refers to herself as "A," leading some of the girls to believe she didn't die.

Co-star Lucy Hale, 21, who plays Aria on the ABC Family drama, tells UsMagazine.com: "I want to know. Even I don't know who it is!"

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Ashley Benson, who plays queen bee Hanna, promises viewers won't be let down.

"I read the eighth book, but only the last chapter because I wanted to know who 'A' was," she tells Us. "We’re staying very close to the books. Everyone who has read the books has been very pleased with them."

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The stars promise even more drama when the show’s final 12 episodes begin airing this September.

"They get blackmailed by someone that can possibly be their dead best friend. You can never fully rest, and so that's what's so great about it," says Bellisario.