AS LOU AND Sadie crept down the hallway, the screaming grew louder, more panicked. It was coming from behind a closed door. When Lou reached for the knob, Sadie gave her a look that asked if she was sure. Lou nodded and pushed the door inward.

Light was flickering from overhead. The sound of a small motor clicked and shuddered. On the far wall, red curtains hung from either side of a large screen. A movie was playing. In it, children were running through dense woods, pursued by someone in a fake-looking monster costume with an enormous papier-mâché mask with giant yellow bug-like eyes and thick fang-tusks that came straight out of its mouth. The movie looked like it had been shot on a phone camera. The screaming the girls had heard was coming from speakers embedded in the walls.

Several rows of seats faced the screen. Gold-painted plaster cherubs decorated the edges of the screen and clung to the walls in bas-relief, as if their playtime had been frozen.

“This is weird,” said Sadie. “I don’t want to be in here.”

Just then, a blond boy sat up from one of the seats and turned toward them. The girls jumped in surprise, but then the boy held up his hands in apology. “I didn’t hear you come in. Sorry to scare you!” He stood and came over, extending his hand. “I’m Cal.” He motioned over his shoulder. “And this is my movie.”

“Your movie,” said Lou, unable to control her sudden scowl. “What does that mean?”

“I made it! Well, me and a group of my friends here in Greencliffe made it. But I wrote the script and directed it.”

“Did you say Greencliffe?” Lou asked. Cal nodded. “Weird. That’s the town where my mom’s family grew up. New York, right?”

“Well … yeah.” Cal looked confused. “That’s where we are right now.”

Lou shook her head. “As strange as it sounds, I’m not sure we’re anywhere right now.” She held out her hand. “I’m Lou. I live in California.”

“Sadie,” said Sadie, keeping her hands to herself. “Toronto.” The girls explained how they’d ended up here—Lou waking inside a giant version of her dollhouse and Sadie’s ukulele sending her into some sort of trance.

Now Cal looked shocked. “In Greencliffe, there are these ruins of an old mansion called Larkspur House. Everyone from my town knows the legends. The place is super-duper haunted. They say that every few years, a group of kids goes missing up at the site. There’re tons of articles about the disappearances online. But I think the ruins are inspiring. In fact, it’s where my friends and I filmed most of my movie. Of course, I had to beg them to come with me.” He glanced at the screen, where the green monster was using a single claw to pin a boy against a tree trunk, then he looked back at Lou. “You think this place looks like your old dollhouse?”

Lou nodded, unsure where he was going with this.

“I’m pretty sure that this house is Larkspur. Or at least it’s how Larkspur used to look, before it burned down.”

“If it burned down,” Sadie began, “then how are we standing inside it?”

Cal shrugged. “All I know is that earlier today, I came back to do more scouting for the final scenes of my movie.” Giddiness shone in his eyes. “When I stepped across the old stone foundation, it was like the ruins had turned back up into a house! I mean … Hello!” He threw his hands in the air. “The walls and floors were solid. They looked brand-new! I had to pinch myself to make sure that I wasn’t dreaming. If I am, it’s a dream come true.”

“So then, this place is Larkspur House,” said Lou. Her mind churned, thinking about her mom and aunt’s conversation. “Since my mom and aunt grew up in Greencliffe, they must have known about the mansion. And all these years later, my cousin disappears around here trying to get to a music academy.”

Cal scowled. “There is no music academy in Greencliffe. Larkspur was once home to an artist and his family, and later, it became an orphanage where a whole bunch of kids died in a fire.”

Lou’s fingers felt numb. The nightmares that had tormented her for the past few months were starting to make sense. Kids trapped in a house, pursued by a monster made of shadow. Or maybe … smoke.

“And you went there?” Sadie asked Cal. “On purpose?”

“I didn’t think anything bad would happen to me.”

“What do you think now?” Sadie gestured to the room in which they were standing.

“This isn’t bad,” said Cal. “This is amazing! I have no clue how it’s happening, but I know for sure that I’ll be able to work it into my movie eventually.”

“We tried looking for an exit,” said Lou. “But the door was locked. And I think the windows are un-smashable.”

“Why would you want to leave yet?”

“Because there’s something here. Something evil. It growls and shakes the floor and the walls and the ceiling. And it’s been chasing us. Haven’t you noticed?”

“Nope.” Cal shook his head, amused. “I’ve been in this room. Enjoying the dark. Seeing my movie on a big screen is amazing.”

The puzzle of this day kept rearranging inside Lou’s head. She was desperate to figure out what was going on. Cal had just provided a bunch more pieces, which made the picture even bigger, more complex. If they could learn what was happening, there was a better chance that they could stop it. “What if we’re inside the ghost of Larkspur House?”

Sadie crossed her arms, as if Lou’s theory had made her chilly. “Do houses have ghosts? I don’t mean just other people’s ghosts. Like, ghosts of themselves?”

“Doesn’t it seem like something that could happen in a horror movie?” Lou asked. “A mysterious force lures some kids into a creepy old house?”

Cal’s face lit up. “Ooh,” he said, his voice low. “Maybe that’s what this is: We’re in a horror movie!”

Lou raised an eyebrow. “I didn’t mean literally. Do you think that sounds more likely than what I suggested about the ghost of the house?”

“We need to find out what’s going on,” said Sadie. “How’d we get here? I hate the not knowing.”

“What’s it matter?” asked Cal. “Whenever you’re ready, we’ll just walk out the front door.”

Lou squinted at him. She didn’t like how he felt he knew all the answers. “I told you we already tried that,” she said, thinking of the five kids trapped in her dreams. “Besides, if this is like a horror movie, as you seem to wish, do you really think the villain would let us go so easily?”

Cal rolled his eyes.

“So then what do we do?” Sadie asked.

“I still remember parts of my dollhouse’s floor plan. Granted, these halls aren’t exactly the same, but they’re close enough. If the doors are locked and the windows are unbreakable, we head for an exit where there aren’t any doors or windows.”

“Such as?”

Lou cleared her throat. “A chimney.” The smile that appeared on Sadie’s face made Lou feel like she was onto something.

“You want us to crawl up a chimney?” said Cal. “Like Santa Claus? Do you know how difficult that is?”

“Not really,” Lou answered. Half joking, she added, “My family doesn’t celebrate Christmas.”

Cal considered this. “Fair enough,” he said, nodding.

Sadie gasped and then nudged Lou toward the movie screen on the wall.

When Lou saw Jason staring at them from inside the screen, her insides turned to gelatin.