A year after their friend disappears, four girls receive mysterious messages from 'A'.

The circumstances surrounding Alison's disappearance continue to haunt Aria, Emily, Spencer and Hanna as questions arise about the night she went missing.

As they try to pay tribute to Alison's memory, the four friends are faced with unresolved issues. With 'A' taunting them every step of the way, can the girls forge ahead and leave the past behind?

Tired of being harassed by 'A', the girls decide to put a stop to the anonymous emails and text messages by blocking all unknown users. But the friends' problems are far from over.

While having to stay apart, Hanna turns match-maker, Spencer exploits her sister’s loss, Emily forges a letter, and Aria is upset in pottery.

Hanna helping Lucas requires Caleb’s aid, while tailing Melissa has an unexpected outcome.

Emily’s swimming prospects could be sunk, along with Hanna’s hopes for the future, while Spencer and Aria make a gruesome discovery.

In custody after a testing day, three of the girls count the cost of the tasks ‘A’ set them to save a life.

To protect them, Caleb and Toby are misled by Hanna and Spencer, while Aria goes out with Holden, hoping to see Ezra.

Mona is messaged by ‘A’ again, Ezra is tempted to leave, and Spencer wants answers from Melissa, but gets distracted.

Jenna’s return brings conflict, Aria agrees to a risky meeting, while a bag of Alison’s possessions seems like old news.

Approaching the second anniversary of Alison's disappearance, a shocking event rocks Rosewood.

One of Aria's past indiscretions is fodder for a new "A." and Emily recalls a crucial event from the night she lost her memory.

Visiting Mona is driving a wedge between Hanna and Caleb and Hanna is forced to weigh up how honest to be with him.

Spencer asks Caleb for help. Aria learns about Ezra's past. Emily is worried about how Paige will be affected by everything "A" has done to her.

A cabin may hold the key to Maya's secrets so Hanna and Emily do some snooping.

Spencer’s misbehaviour causes concern, Hanna engineers an encounter Caleb is resisting, Emily’s detective work turns dangerous.

Det. Wilden seeks to silence those who know his secret, the heat is on for Spencer after reengaging with Wren, and Ezra’s mother tries a new angle of attack.

Some secrets of Mona’s asylum stay come to light, a corpse must be faced, and a lost child tracked down.

Still living at a motel, Emily is taken aback when Ali's mother offers to let her move into Ali's old room and is shocked when the other Liars insist Emily take up the offer.

After being blackmailed by A.D., one of the Liars begins to supply info to the dark side in order to protect those closest to her. Detective Furey questions how much the PLLs know about what happened to Archer Dunhill. Aria tries to issue an ultimatum to Ezra in regards to Nicole, while Emily struggles with how to support Ali. Spencer goes to elaborate lengths to meet up with Mary Drake and encounters Wren. After learning something surprising about Lucas, Hanna sets out to prove her friend is innocent and uncovers even more troubling info.

All is revealed as the ultimate endgame comes to light.