'A' is for Answers

S4 E24: In the fourth season finale, after years of questions and mystery surrounding the night Alison DiLaurentis disappeared, her four best friends come face to face with Ali and finally learn what really happened to her that September night. Now, with their newfound knowledge of Ali's long-held secrets, can Aria, Emily, Hanna and Spencer help Alison finally figure out who "A" is?