Night.
It's the period of time between the sunset and the sunrise when the Sun is below the horizon. On first sight, it might be seem, that in night nothing happens. It's quiet, it's dark, people's sleeping. However, generally, in the night the biggest parties are taken place, the most murders are committed, the most secrets are revealed. One of those secrets has been revealed that night. In a small town called Gravity Falls by two 12 old siblings. Those two siblings were me and my sister Mabel.
"Not only Gravity Falls is not what it seems" I said.
"Grunkle Stan is not what he seems too" Mabel finished for me.
We stood in hiding still for about 2 minutes. After a while, we awoke. In the dark room, we walked to the machine. We looked on the vending machine very closely. It looked... normal. Chips, chocolate bars, drinks. All this stuff were closed behind glass. On the right side, there was small display and eleven buttons, 1 to 9, 'Select' and 'Cancel'.
"And... What's now?" I asked
"I don't know, it's so weird" my sister answered, "Stan pressed buttons, maybe it's a code or something?"
I started thinking, "How to open this and which button press?", I pressed "1". "Flip coins" appeared on the display. I repeated pressing with others buttons. Nothing special, "Flip coins". "This does not make any sense, how we will guess the code?". We didn't know what to do. There were lot of possibilities.
"I know, some time ago I found a secret code on the Fight Fighters machine" I recalled myself, "Mabel! Maybe a tip is written on this machine?"
I looked closely at every single part of the vending machine. Nothing. I checked right and left side. Nothing again.
"We will never open this..." I said depressed.
"Hey, I've done it!" said Mabel suddenly joyfully.
"You what...?!"
Indeed, On display there appeared three horizontal lines.
"How did you do that?!"
"I held the Cancel button" answered Mabel with smile.
"You held the Cancel button...?" I felt a little embarrassment.
"But what is that means?" she asked.
"I think...It's empty space for the code. 3 lines, 3 numerals"
Another problem. There were one thousand permutations. Is it random number? Or maybe it's a date or his lucky number, or something? I looked around the room like I thought there was a tip.
"Mabel, maybe Stan wrote the code on paper and hid? He is so forgetful" I proposed her.
"Fine" Mabel agreed.
Only then it came to mind, we could turn on the light. Bright light scattered all over the room. We started looking for any tips. Mabel walked to shelf gifts. I walked to cash register. We was looking for ten minutes. I glanced on the clock. It was 11:10pm.
"There's no anything!" said Mabel.
I opened one of the drawers. Mainly, there were just bills. Water bill, electricity bill, nothing special…
"I guess, we won't find anything here, let's try put th…" I interrupted. On every bill, I noticed something…

"Stanford Pines
618 Nathaniel Street
Gravity Falls, Oregon, OR 438631"

"618… 618, of course! It's a code! An address!"
I ran to the vending machine.

SIX…
ONE…
EIGHT…

I heard a sound and the vending machine moved.
"Yes! It works! Dipper Pines, you're a genius!" I said to myself.
The vending machine opened and then I saw a stairs. Stairs which led, to a unknown to me, corridor. I was so excited. At that time I could go to discover a truth. That corridor was my gateway to answers on my questions.
"Mabel, what are you doing? Come here now." I called her.
Mabel walked to me and she saw that entry.
"Oh, my goodness. So cool!" she was thrilled, "Ok! Let's go!"
And then she ran to the stairs, "Dipper! C'mon!" she yelled.
"Ok, I'm coming" but I had a strange feeling. Me and my sister went down.

Stairs dragged for a long time. There was so cold and unpleasantly. Small lights were hung alternately, on the left and right side of walls. And then I heard a crack from the top. Mabel groaned slightly, but it turned out it was just the vending machine, which it closed. A little bit of light, which was coming into a corridor disappeared.
"Hey Dipper! Let's sing something!" Mabel proposed.
"…No?"
She made indignant face.
After a while, I noticed the stairs were over. The corridor split into five passes. On the walls of every transition, except one of them, there were small letters arranged in Exit writing. In front of me I saw an arrow. The arrow pointed a way. The way was not visible. My sight couldn't reach the end of the corridor. Mabel proposed we should follow the arrow. I agreed with her. The total silence was disturbing us. Creepy mood was stimulating my imagination. I almost could hear Mabel's scream and her terrifying face from my dream again, when I looked on her. "Well, keep going forward." I was trying don't look at her.
"Look… the tiles." Mabel noticed.
Concrete, cold and moist floor, suddenly, was lined by white and green tiles. Messy and leaky walls were replaced by smooth, elegant, white walls. Immediately, atmosphere changed from worrying to calmer. Even lights became brighter, unless it just seemed to me. However, it was so suspicious.
"I feel like I was in the clinic." said Mabel, "Hey, look! I finally can see something!"
Out of dark space, undefined shape came out.
It was just door. White door.
We looked at each other. "But what if he's there?" Mabel feared, "I think, we should follow him so that he didn't saw us"
"We must risk" I said.
We took a deep breath and then I put my hand on the handle. I felt its cold. I pressed the handle. It made creak. We felt increasing edginess. We heard loud beat of our hearts. I finally opened the door. Anxiety, that someone was there, disappeared. There were nobody. I mean, I thought… In whole room was dark. We walked into room and Mabel found a light switch. I was right, there were nobody. It was big, light room with the same tiles and walls like at the end of that corridor. On the middle there was big table and six chairs. Next to me I saw stairs leading to the top. There were also a small television and a couch. On right side there were bookcases. It was look like a dining room and living room. Me and Mabel started to look around.
"Why Grunkle Stan decorated… a living room underground?" I said
"Maybe he was fed up with us and he's hiding from us" Mabel joked.
There were three doors. On one of them was written "WC", on the second one was written "Kitchen"
"Did he build a house?"
The third door was the biggest. Inscription on it didn't say it was a normal room. On the third door was written "Laboratory".
We was looking at it for a little while. And then the silence was broken by voice.
"Hey! What are you doing here?!"
We recognized the voice, but we had to turn around to believe it was true.
"You shouldn't be here" said Soos.
Yes… It was Soos. I wanted to ask the same question, which was asked by him.
"Soos! What is this place?" asked Mabel.
He made a depressed expression.
"Look dudes, it's … a little complicated, I..I.. promised don't tell anything. Mr. Pines said it's for the good of all."
Me and my sister's eyes were so big. We didn't know anything and were shocked at the same time.
"Soos? Who are you talking about?" It was Stan's voice who came out of the laboratory. When he saw us, he made a appalled face. In his eyes I saw despondence, fear and rage at himself.
"Soos… Did you bring them?" said Stanford with calm.
"No Mr. Pines, really! They were here, when I came out from the WC"
Stan was rage at himself so much.
"I could check is someone follow me when I came here more precise. Or maybe I should have set more difficult code…"
I still didn't know anything and I could not stand it anymore.
"GRUNKLE STAN! Tell me, now! What is this place? What are you doing here? Why are you hiding from us?!"
I never thought I've ever yell at someone so hard like this.
Stan was silent for a moment. And finally he said:

"Let's say: We have a little problem with Gravity Falls"