The summer was over and it was time for Dipper and Mabel to leave Gravity Falls behind, at least for the time being. With some luck, they might be able to convince their parents to let them go back for a visit around Thanksgiving, or maybe for Winter Break. Spending Hanukkah with their Gruncles would definitely be a blast. The twins were sad to leave. They'd had such fun adventures there. Now, they were going to start their first year of High School. For many, that sounded like an adventure, but after what the two of them had faced, it was just a drag.

As they said their tearful goodbyes to their new friends and to their Gruncles, Dipper couldn't shake a bad feeling. Something was wrong. He couldn't place his finger on it, but something was definitely ominous about the ride home. Like they were being watched.

"Mabel, do you feel that?"

"What?"

"Like we're being watched."

"We're on a bus, Dipper! There's nothing to do but people watch. I'm sure it's nothing to worry about- just some of these friendly bus travelers trying to pass the time."

"If you say so..."

The bus ride took forever and by the end of it, Dipper felt sick with worry. Mabel's words hadn't soothed him. Not to mention Waddles had been agitated the whole trip. Pigs had good senses! Dipper was now positive something terrible had followed them back from Gravity Falls.

"Welcome home, kids! How was your summer?"

Their parents rushed forward to greet them with a warm hug.

"It was great, Mom!" Mabel chimed jovially, "I got a pig- his name's Waddles- and we had so much fun with Soos and Wendy and Gruncle Stan and Gruncle Ford and Candy and Grenda and-"

"Whoa, there, Mabel! Tell us about it over dinner. We whipped up a special welcome home spread!"

"Hooray!" Mabel grabbed Dipper's arm and pulled him inside. "C'mon, brobro, let's eat!"

Dipper just pushed his food around with a fork all night. Something was off. Unfortunately, his father noticed.

"What's wrong, son? I'd expect you to be starving like your sister."

"What? Oh, no, I'm fine, Dad. Just a little sick from the bus ride. I just need some fresh air."

"Give the rest of your food to Mabel's pig, and put a jacket on before you go out."

"Yep."

Outside, it was cold and loud. Cars drove by, the neighbor's dog was barking incessantly, and Dipper could still hear Mabel through the sliding glass door that led to their yard, yapping about the summer. He should be with her, sharing in the excitement, but he just felt so terrible. Why did he feel so terrible? The summer had been great. Was it like anti-homesickness? Did he miss Gravity Falls more than he wanted to be home? No, that wasn't it. He knew he'd readjust quickly, and that he'd be able to see his Gravity Falls friends soon enough. So what was the big idea?

Dipper gave up trying to figure out what was wrong, wrote it off as puberty, and went to bed. Mabel was already there, laying in her top bunk and scribbling with crayons in a notebook.

"Dipper, look! I drew a picture of Waddles eating Gruncle Stan's favorite slipper. Remember that?"

"That's great, Mabel." Dipper wasn't really looking at the drawing.

"You look sick, Dip. Maybe we should hit the hay, huh?"

"Yeah."

Mabel turned off the light, snuggling closer to her stuffed animals.

"Night, Dipper."

"Night, Mabel."

Dipper's mind ventured to ungodly places that night, depicting images of their worst encounters in Gravity Falls until finally all that remained was Bill's mad cackling over a dark landscape. As the moon rose over the land, a lake was revealed, the moonlight reflecting on the tips of the waves and spelling out, "YOU THOUGHT YOU WERE RID OF ME" over and over.

Dipper woke up screaming. Mabel had to climb down and calm him. He didn't sleep again.

The next morning, Mabel followed Dipper out to breakfast, helping him to avoid tripping over obstacles in his sleep-deprived, zombie-like state. She'd have to sneak him some Mabel Juice.

"Kids, we have a great surprise for you! We're getting an exchange student. He'll be staying with us and going to your school!"

Mabel forgot all about the juice. "Really?" She squealed excitedly, "What's his name? How old is he? Is he single? Oh my gosh oh my gosh oh my gosh!"

"Kids, I'd like for you two to meet Billy! He'll be a senior this year. Isn't it great?"

The twins' jaws dropped. Their parents had invited sin into their household. Mabel hissed.

"Mom we have to get rid of him right now immediately."

"Mabel, I'm surprised at you! Don't be rude- poor Billy just got here, and you're already being mean?"

"But he-"

"No buts, Dipper! That goes for you, too, Mabel. Treat our guest with respect. It's only until summer."

Dipper died a little inside. Their guest room was going to be occupied by a demon with greasy yellow hair, a plaid track jacket, a tee shirt with a bowtie printed on it, and a shitty little tophat barrette clipped to one side of his head.

'Bill Cipher dresses like a fucking train wreck. He clearly doesn't know how to behave in the human world. How did he acquire a physical human form? What poor fool is he using as a puppet? I must help them before their high school life is destroyed.' Dipper would try and contact the body's spirit later. For now, they had to go back to school shopping.