Pretty Little Liars season 6
Sara's mysteriuos absence during Charlotte's death sparks the speculations that she might be the culprit Freeform

In the previous episode of Pretty Little Liars season 6, fans got to see a mysterious old man keeping a watch on Emily's movements. The man, at the end of the episode, boarded a car and removed the mask that made him look old. This has made matters more dubious in Rosewood.

Warning: Potential spoilers ahead

Moreover, while suspicion was initially on Ezra, Aria tried to find proof against her former teacher's involvement in Charlotte's death. However when she failed, she realised that the nine iron – the weapon used to kill Charlotte – was not the one that was seen on Ezra's loft. This ignited speculation that Sara Harvey, who showed up at Charlotte's funeral in episode 11, could be the behind the threats.

In the upcoming episode titled Do Not Disturb, Spencer and Aria will team up to investigate Sara's involvement in the murder. Meanwhile, Hanna will team up with Caleb to find the stalker who is sending threat messages to the liars.

Below is the the synopsis of the upcoming episode:

In order to prove Sara Harvey is behind the threats, Team Sparia reunites to find evidence of Sara's involvement before they go to the cops. Caleb puts together a plan with Hanna to fight back against the new stalker by using the security footage tapes.

Meanwhile, Aria gets unexpected news from her family, and Ali comforts Emily in her time of need.

The episode will also feature an intense scene between Spencer and Mona Vanderwaal (Janel Parrish), who teased that it will not be "pleasant". "She is always a little shady and you never know what her real intentions are but I think that is what makes her such a fun character. She will be back on Tuesday and she will have a run in with Spencer that will not be pleasant for Spencer," Parrish told Hollywood Life.

She spoke about the next A as well. "I know who the new A is, and I can't tell you that! Well, actually, do I know the new A? I have a pretty good idea who it is but our writers never tell us anything," she said.

Pretty Little Liars season 6 episode 15 will air on 9 February on Freeform. Click here to watch the show live on Freeform (only in the US).