Alison, Mona, and the liars all make a plan to bring down Dana Booker. 

Ava deletes Dylan's plagerized submission before his professor can see it. 

Mona and Taylor don't take well to each other. 

Mason asks Mona to play chess in person. 

Ava and Zach share a moment which causes her to flashback to a time between her and Nolan. Ava tells Zach she'll catch up to him on the way to class. 

Dylan's professor got his submission and is going to submit it into a contest. 

In preparation for the mixer, Mona and Taylor use an app to decipher what it sounds like when Dana is telling the truth so they can tell when she's not. 

Zach goes to check on Ava who never showed up for class, but she's drunk and wearing Nolan's shirt. 

Dana offers to solve all of Dylan's problems if he rats out his friends. 

Caitlin tells Ava that she thinks Jeremy is keeping something from her. 

Alison meets up with Gabriel, the language professor, and he gives her a dance lesson.

Mona tells Mason that they can't do anything more than play chess. 

Dylan yells at Ava because he believes she didn't successfully delete the file. 

At the mixer, Taylor appears upset when she sees Alison with the language professor. 

Jeremy claims he has to work, but Caitlin follows him to see what he's up to. 

Dana comes to Dylan's who appears to be ready to rat out his friends. After she leaves, Ava and Mona come out of hiding and reveal they have everything Dana said on recording. Dana admitted that she would give Dylan a fake alibi, which is a felony.

Alison and Gabriel kiss, but she finds out that he's married and in an open relationship. Alison tells him that she doesn't want any more drama in her life. They agree to still be friends. 

Caitlin watches Jeremy destroy his laptop and throw it in the water. 

Mason goes to Mona's and tells her he can't stop thinking about her. They end up having sex. 

Taylor tells Alison she wants to be the one who gives her mom the evidence about Dana.

Jeremy tells Caitlin she shouldn't have followed him and to get in the car.