Pretty Little Liars fans should expect to learn more about Spencer (Troian Bellisario) when the ABC Family series returns for season 4B in January.

Bellisario spoke with E!Online about a special secret viewers will learn about Spencer in the latter half of Pretty Little Liars season 4.

"What you're going to see in 4B is a very, very interesting secret that you never knew, that we never talked about with Spencer." Bellisario teased. "It really, really affects her relationship with Toby [Keegan Allen] and with the girls, and it reveals a lot about why she wasn't passed out with the other girls the night that Alison [Sasha Pieterse] died. I'm so excited we're finally getting into that, because I've been waiting for seasons to get into that."

Details on Pretty Little Liars season 4B are gradually leaking out through the show's various actors and executive producers.

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Ashley Benson, who plays Hanna on the series, teased that the season finale would be "insane" and potentially cause a change in the show going forward.

"I think a lot of people are going to like it. All the questions will be answered," Benson said. "I can't tell you much more because I don't want to ruin it, but it's really good and season five is going to be completely different. People are going to be pretty shocked."

Pretty Little Liars returns for season 4B on Tuesday, Jan. 7 at 8 p.m. on ABC Family.

Watch a preview of the next episode of Pretty Little Liars here:

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Pretty little liars, Spoilers