Pretty Little Liars Season 5: Is Mona's twin sister coming to Rosewood? A's mysteries to unravel during finale
Emily, Hannah, Spencer and Aria in ABC's teen thrillerPretty Little Liars/Facebook

Pretty Little Lairs season 5 is becoming interesting with each passing episode as the identity of 'A' is left fans puzzled.

Currently the focus is on Aria's little brother Mike, who appears mysteriously and his actions have almost convinced many fans that he could be 'A' or at least working under his/her guidance.

Cody Christian, who plays Mike, has teased that the identity of Rosewood's most feared villain will be revealed soon and the final of PLL 5 will be a big one.

"You'll definitely know why Mike Montgomery had his name on the visitor log. Mike's really starting to expand as a character, so he'll have different scenes with a lot of different characters coming up," Christian told MTV.

"It's a big one. You will never forget this finale, I promise you," he added.

Meanwhile, Aria has doubts about her brother and will seek Andrew's help in keep a tab on him. But according to the show's synopsis, she will get a shock when she discovers something related to Mona's murder.

The official synopsis of episode 20 reads:

Determined to get college tuition money without the help of others, Hanna pushes forward with her quest to win the local beauty pageant and hires a pageant coach to ensure her win. Quickly learning that you have to be more than a pretty face to win the grand prize, Hanna turns to Emily for help. Also needing a little help, Aria asks Andrew to help keep tabs on Mike, whose increasingly suspicious behavior suggests a chilling connection to Mona's death. What Aria ultimately discovers, makes her blood run cold.

While the season is inching to its finale, fans are coming up with different theories and one of such theory suggests Mona's return to the show as her twin sister.

"I know who Big A is as they will be revealed in this season finale. It will be Mona's twin. Janel [Parrish] said she would still be a regular next season but 'in a different way.' Big A will be revealed to the audience this season finale but not in a way we are expecting, according to the actor who plays Mike," Kpopstarz reported.

Further on the show, Spencer decides to help Jonny on a less than legal adventure.

Pretty Little Lairs season 5 episode 20 titled 'Pretty Isn't the Point', will air on 17 February on ABC Family.