In this heart-stopping preview for the episode, "A" starts sending messages to Mona (Janel Parrish), and we find out the girls might actually learn the truth about Alison's (Sasha Pieterse) death. Talk about game changer.
Watch the preview here. Heck, watch it twice, or ten times — we certainly did!
Be sure to tune in for the next episode of Pretty Little Liars on Monday, February 20 at 8 pm ET/PT on ABC Family.