13 of the Most Terrifying Moments From Pretty Little Liars

Seeing Ian's lifeless body hanging in the bell tower gave us nightmares for DAYS.

The reveal in and of itself was terrifying. It was crazy to see this whole new — and, well, crazy — side of Mona. It wasn't simply that she was vengeful, it was that she was utterly maniacal. We'll never forget that haunting shot at the end.

Any time the show features creepy dolls, you can bet we'll lose sleep.

The whole Halloween episode in season three really is a "dark ride," as the episode title suggests. Garrett Reynolds gets murdered, and Aria winds up in a box with him. Perhaps the creepiest character, though, is the masked Queen of Hearts, who haunts the train all night long.

The whole sequence reads like a horror movie: Spencer wanders the darkened halls of a sanitarium, following some sort of entity. The strange, contorted dance moves of Maddie Ziegler only make the scene that much more chilling.

In the fourth season, the Halloween episode takes us all the way to Ravenswood, where madness and horror walk the streets. We've seen our fair share of masked villains on the show, but there's something about Gas Mask man that's so, so unsettling.

At the beginning of season seven, Hanna's been captured by "A.D." Not only is she imprisoned in some sort of hellish barn, but her captor also taunts her with a cow prodder. It's the stuff of nightmares.

It's not just that Rollins dies, it's that he crashes through the girls' windshield. Just look at that dead, lifeless stare and try to tell us it's not burned into your memory.

Once the girls find themselves in the massive, labyrinthian dollhouse of "A," things really take a horrific turn. They wake up having been surgically implanted with tracking devices. Spencer regains consciousness covered in blood. In other flashbacks, Emily is forced to shock one of her three friends. It's the purest sort of ghastly torture.

It's not until the end of this episode that we find out the truth of Ali's breakdown. She's not being visited by Wilden and Jessica DiLaurentis's ghosts; it's just Mary Drake and Dr. Rollins in disguise. Even so, before the truth is revealed, it's like Ali's living a real-life zombie apocalypse, and the terror for the audience is just as real.

This goes down as one of the most brutal physical attacks we've seen on the show. Not only does Ali get bruise marks on her neck from that "A.D." chokehold, but she gets slammed into a mirror as well. That's more than enough to leave you jilted.

There's something creepy about Mrs. Grunwald. She's pretty harmless, but her voice, her piercing eyes, and her cryptic way of speaking are all enough to give you the creeps. She always seems to pop up at the show's most chilling moments, materializing like a ghost.

Man, did Pretty Little Liars really up the stakes in season seven or what? After the grisly, windshield-smashing death of Dr. Rollins, Noel Kahn loses his head in an unfortunate and clumsy scuffle with the girls: he falls on his own ax. We can't say we'll miss him, but we can say he'll haunt our dreams.