Four 16-year-old girls believe their secrets are safe forever after their friend mysteriously vanishes, but the truth may be only one text away.

A young woman is stabbed to death and dumped in a forest. The woman's best friend is the prime suspect, but could a third party be involved?

With the return of Jenna Cavanaugh to Rosewood, the girls must face an unpleasant past as questions arise about Alison's death.

Old and new relationships are examined as the girls try to pay tribute to Alison's memory. But with A taunting them every step of the way can the girls leave the past behind?

When Tristan and Rory are cast as Romeo and Juliet in the school play, a green-eyed Dean insists on going to every rehearsal, and Lorelai endures Luke's teasing after she dates a much younger guy.

Last-minute preparations for Alison's memorial get derailed when her brother, Jason DiLaurentis, arrives back in Rosewood.

The girls are trapped at school as a bad storm brews, and tensions run high. Plus, Byron leans on Ashley for advice on parenting as his relationship with Ella takes a bad turn.

"A" instructs the girls each to perform a specific task or Dr. Sullivan will be killed; Emily is lured into a deadly situation.

It's the Halloween before Alison went missing and the friends hope to score an invite to Noel's Halloween party.

When a surprising new victim of A is revealed, the PLL's small group may get one person larger. Meanwhile, Wren comforts Spencer through family issues as Ezra's new opportunity pushes him from Aria.

Caleb's involvement in cracking A's phone has had Hanna worried from day one and now A is determined to punish him for it. Meanwhile, the police are looking for Caleb's computer.

Officer Wilden wants to test Hanna's blood; Mona passes along secret messages to Hanna and Aria; Spencer covers for Jason after he gets drunk and has a car accident.

Hanna's visits with Mona do not sit well with Caleb; Aria dreads telling Ella that Byron is dating Meredith; Spencer seeks the truth about Melissa.

One father has a guilty conscience, one has a daughter he doesn't trust, one is hiding a secret from his daughter and the other is MIA, it's not the ideal time for the annual Father-Daughter Dance.

The girls believe that "A" will strike at Jenna's birthday party; a heartbroken Hanna makes a shocking discovery.

A major clue from Garrett sets Hanna and Spencer off on separate missions; Emily experiences another flashback from "that night"; Ezra's sudden influx of cash catches Aria's attention.

Gibbs is forced to revisit his painful past when his former mother-in-law turns out to be a witness in a murder investigation.

Despite Spencer's brave face, Aria, Hanna and Emily remain concerned about their friend's health; shocking revelations are revealed.

Aria contemplates telling Ezra about his son; Hanna suspects that Caleb is keeping a secret from her; Spencer no longer wants to play games; Emily learns more information about Ali.

Spencer is ready to talk; Ashley is involved in a hit-and-run accident; Hanna hides a new secret; Aria contends with Ezra's new life with Malcolm.