The students show up to class only to discover that they have been invited to a cocktail party at the Professor's house. Their invitations contain secrets— ones that they are not allowed to share with anyone else. Of course, the Party Twins and Alvaro alliance immediately breaks the rules. Once at the house, the Liars Club discovers that their task is to return that secret to its rightful owner, forever binding them together. When Bella and Benedict's cheating is revealed, however, more secrets spill forth.

While Moynihan expresses his confidence in Cuff to a local journalist, Cat's is badly shaken. She discovers Allie and Harper confiding in each other about the Liars' Club case and feels betrayed by her only friend. Left vulnerable and even more alone, Cat becomes the prime suspect when a video of her actions the night of fire is emailed to every student on campus

The Liars' Club gets a chance to use Cuff on each other, testing the truth of their alibis. Things go askew, however, when the device proves Erika's honesty: she was outside the administration building at the time of the fire, and she saw someone who looked like Wilson running away. Adding to the upheaval is Margot Miller's recovery from her coma. Suddenly, there's someone else who might have information about everything leading up to the fire. The Liars' Club may have narrowed down their suspect list, but the mystery is far from being resolved.