Lucy Hale, Shay Mitchell, Ashley Benson and Troian Bellisario gather around a laptop in this new still from Pretty Little Liars.

In tomorrow’s season finale “For Whom The Bell Tolls,” now that Aria, Emily, Hanna and Spencer are in possession of the information that Alison left them, the girls decide that it’s time to finally put an end to “A” and the mystery surrounding their friend.

But without certain proof that their hunch is right, how can the girls catch “A” in his/her own game? And with little more than a video and hazy memories of the night that Alison (Sasha Pieterse) disappeared, the Liars may have to turn to an unlikely source of information to help them put a stop to “A” once and for all – or so they think.

“For Whom The Bell Tolls” premieres Monday, March 21st @ 8PM ET/PT on ABC Family. 10+ pics inside…