It is time for ex-lovers Caleb (Tyler Blackburn) and Hanna (Ashley Benson) to reunite and track down the sender of the mysterious text she and the other girls received about Charlotte's (Vanessa Ray) murder in the upcoming episode of "Pretty Little Liars."

In "Do Not Disturb," CarterMatt reports that Caleb will have a brilliant idea to use the tapes of the security footage to determine the Liars' new stalker. Shortly after Charlotte's death, all four — Hanna, Spencer (Troian Bellisario), Aria (Lucy Hale), and Emily (Shay Mitchell) — got a message warning them to speak up about the accident, as they know who killed Charlotte. The threatening message was reminiscent of "A's" modus, and the girls were alarmed.

They have a suspicion that it was Sara (Dre Davis) who sent them the text. The blonde, with her black gloves and enigmatic actions, draws no love from the Liars, even if she looks sorry for everything that they have been through. Aside from Caleb and Hanna, Spencer and Aria will also take it upon themselves to conduct their own investigation.

Team "Sparia" wants to know what Sara is hiding. The promo shows Aria using her camera stick to take a picture of the girl's hotel room. Not content with what she has done, Aria asks Spencer to come with her and cross over to Sara's place via the balcony window. Elsewhere, their target is convincing Alison (Sasha Pieterse) that she is innocent. Sara is seen going to the blonde's classroom and tearfully telling her she is the only one who stuck to Charlotte when everyone shun her.

Meanwhile, trouble is brewing for Emily. The teaser shows her screaming for help. The girl clearly needs help, but she cannot tell her friends about her problem. Meanwhile, Aria will have to see her dad, Byron (Chad Lowe), who badly wants to talk to her. Does it have something to do with the fact that he has become one of the primary suspects in Charlotte's murder?

"Pretty Little Liars" season 6 airs Tuesdays at 8 p.m. EST on Freeform (formerly ABC Family).