The girls try to pay tribute to Alison's memory, but they are still faced with unresolved issues. Aria has an unpleasant encounter with her father's former mistress, and Spencer must face a vengeful Melissa. Hanna is trying desperately to get her boyfriend to forget the 'old Hanna'. But with "A" taunting them every step of the way, the girls will find that leaving the past behind is much harder than they first thought.