Pretty Little Liars
Pretty Little LiarsPretty Little Liars/Facebook

The identity of A is still unknown to the liars, but they will be relentless in their mission to learn more about the villain. In Season 6 Episode 15, Spencer (Troian Bellisario) and Aria (Lucy Hale) team up to find out if Sara Harvey (Dre Davis) is indeed their tormentor.

In last week's episode, Aria found her father's nine iron, the weapon used to kill Charlotte, missing from their house. Furthermore, Byron (Chad Lowe) was sketchy about his whereabouts while talking to his daughter. Is he somehow connected to A and Charlotte's death? At the end of Episode 14, the liars found a hoodie, gloves and a cellphone, and an ominous message from A, stating: "I don't lurk in the shadows. I hide in plain sight."

In the promo for the upcoming episode of "Pretty Little Liars", Sara Harvey is seen wearing a pair of black gloves as she enters Alison's (Sasha Pieterse) classroom. Sara talks to Ali and they discuss Charlotte and her death. The promo indicates the two will perhaps become friends at the end of their conversation and may team up as well. However, their reasons for doing so aren't clear yet. Sara has been on the liars' radar since the mid-season premiere of Season 6. It remains to be seen if they do indeed find evidence pointing to her as the killer.

The sneak-peek video also indicates Spencer and Aria will undertake a dangerous mission to uncover A's identity. Aria seems convinced Sara is A, and asks her best friend to break into her hotel room. When they finally gain entrance, Spencer finds drawers filled with gloves. She looks shocked as she grapples with this new-found evidence.

Season 6 Episode 15's synopsis on TV Guide reads:

Team Sparia reunite to search for evidence that Sara Harvey is behind the threats; Caleb and Hanna make a plan to fight back against the new stalker using the security-footage tapes; Aria receives unexpected news from her family; and Ali comforts Emily.

"Pretty Little Liars" Season 6 Episode 15, titled "Do Not Disturb", airs on Tuesday, February 9 at 8 p.m. on Freeform (previously known as ABC Family). You can live-stream the episode here.

Watch the promo here: