Tambry poked her head out of the door from and looked down the hallway. She turned her head and glanced back and forth before stepping aside to let Mabel and Wendy in. They quietly darted down the hall and stopped at the door at the very end that bore a golden star with the words "The Background Guys" written in black text.

The girls quietly squealed as Tambry twisted the doorknob and pushed open the door. Stepping inside, they stared in awe at the room around them.
It was surprisingly bigger than what they had expected with clothing racks that lined each wall and five sets of vanities in the back corner.

To their left was a snack table that Mabel decided needed to be investigated while Wendy and Tambry left to examine the rows of autographed photos of celebrities that covered an entire wall.

"Woah. . ." Wendy whispered. "Can you believe this place?"

"I know right." Tambry scanned the wall. She paused and laughed. "Look! Babba!"

Mabel turned, wiping crumbs from her hands. She laughed, pulled out her phone and snapped a photo.
"Dipper's not going to believe it!"

"I don't think it's the best idea that anyone knows about this, actually," Wendy pointed out. "Do either of you have any idea how much trouble we could be in?"

"Nah," Tambry said. "It'll be fine as long as we're not caught."

Mabel nodded in agreement. "Like Stan always says. 'Anything's legal as long as cops aren't around.'"

"I don't know-" Wendy was cut off by a sudden scream from the opposite side of the room.

The girls fell silent, eyes widened.

"What was that?" Wendy whispered.

She spun around and stared at the direction the scream had come from. The only possible answer was the door that stood by the vanities.

Wendy slowly approached the door with Mabel and Tambry at her heel. Wendy tried turning the knob, but the door had been locked. Tambry solved this by picking the lock with a hair pin. When the door swung open, the girls held back screams.

In the storage closet sat three girls, tied by their wrists and ankles with tape covering their mouths. One girl had managed to tug away the tape over her mouth to cry for help. Wendy noticed that the girls each had a backstage pass around their necks.

"Help!" the girl croaked. "It's the band-"

"-what happened to you?" Mabel gasped.

Tambry bent down to untie them and Wendy helped by removing the tape from their mouths. The girls sat up and scooted together in a huddle, shaking in fear.

"It's the Backstreet Guys! They're-they're, monsters!" one girl exclaimed.

"What do mean by monsters?" Mabel asked. She was already reaching for her cellphone again to text Dipper.

"They started singing and then they tied us up but we didn't do anything. We couldn't stop them. I don't know how, but they hypnotized us or something."

Wendy looked at Mabel fearfully and said, "what do you think?"

"I'm calling Dipper," she said. Her thumb wavered over the call button when the door to the dressing room burst open.

The girls screamed again. Tambry shushed them, pulled Wendy and Mabel into the closet, and shut the door.  They each held their breath and scooted backward until they were all pressed up against the back wall.

Mabel held the phone up to her face, her hands shaking as she whispered "come on come on pick up the phone. Come on come on pick up the phone."

. . .

Dipper wasn't sure how long he had been sitting on the side of the road. He woke up to the sound of his phone vibrating in his pocket. He sleepily picked it up and answered the call.

"Mabel?" he croaked.

"You have to come to the stadium right now," came Mabel's voice in a hoarse whisper.

"What's wrong?" Dipper said. He sat up and put a hand on the steering wheel.

"The Background Guys are some sort of monster."

"What kind of monster are we dealing with?"

"I don't know. . . they seem to hypnotize girls when they- Dipper! They're sirens!" she exclaimed.

"Are you sure?"

"Yes! They have us trapped in the dressing room-" she suddenly stopped and she screamed. Dipper felt his stomach churn when the line went dead.

He instinctively dropped his phone, slammed his foot against the gas pedal, and made a sharp u-turn while the cars around him honked and yelled in protest.

As soon as he pulled into the parking lot, he leapt  out of the car and slammed the door closed. He typed on his phone as fast as he could manage, trying to research as much about sirens as he could in a matter of seconds, but to no avail. His heart was pounding fast and his brain was clouded with panic.

He found that the backdoor was propped open, making it oddly easy to enter the building. He followed the trail of arrows and signs that directed him towards the dressing room.

Dipper pressed an ear against the door and waited. He heard nothing but silence. He had been expecting to hear muffled screaming and shouted. For a second he began to wonder if he had the wrong room.

Finally, he pushed open the door and slowly stepped inside the dim room. His eyes scanned across the rows of costumes and framed photos until he focused on the door to a storage closet. As he approached, he noticed an axe laying on the floor. It was Wendy's axe. The one she always carried in her back pocket. He picked it up and held it above his shoulder like a baseball bat.

Slowly, he opened the door to see five teenage boys in matching stage outfits staring back at him. The one in the center, wearing a leather jacket smirked and whispered, "boo."