"Pretty Little Liars" is back on ABC Family for the sixth season. Tune in on Tuesday to watch the season premiere.

In the Season 5 finale, "A" gave Mona a gas mask that she never uses, Entertainment Weekly noted.

"A/Charles never gives a present without a reason behind it. In fact, Janel Parrish assures fans that the gas mask will play an important role when season 6 returns with the girls still trapped in the dollhouse," EW's Jess says.

Parrish says although Mona "will be treated differently because she is [Charles'] favorite," that doesn't mean that Mona will be off the hook. "[Mona] will ultimately still be punished," Parrish spoils.

In the season's premiere poster, Mona is wearing the gas mask, indicating that she will have to use it at some point in the series, Spoilers Guide notes.

"PLL" actress Sasha Pieterse talked to Zap2it about the next season explaining a few more details about A, a mysterious character who has been terrorizing her and the Liars for years.

"She has no clue who this person is. I'm pretty sure I'm able to say that," Pieterse says. "It's completely a shock to her [when she finds out Charles is A]. And so, that also brings up if Charles is somehow related to the DiLaurentis family, how come no one knew about him?

"That unravels a whole other different but cool storyline actually because as much as everyone knows what's happened and the girls are trying to figure it out, they're also following their own story line and their own demons."

What will the Pretty Little Liars find out about "A"? Exactly how is he related to the DiLaurentis family? How will the girls escape the dollhouse?

Tune into ABC Family on Tuesday at 8 p.m. ET for the Season 6 premiere of "Pretty Little Liars" to find out.

Related