With just one episode remaining until the Pretty Little Liars season finale, this ABC Family hit will tease the concluding events to come on Monday's "Monsters in the End."

What can viewers expect from this installment? The show is notoriously tight-lipped about specific spoilers, but look for Emily's discovery of a garage door key to play a major role, while Spencer finds herself freaking out inside a dark room.

Check out our review of last night's "Someone to Watch Over Me" and then prepare for what's ahead via the following official trailer:

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.