Where was I?

I don't know where I have been for the past month. I opened my closet door, like that freak told me to do, and I looked inside. I expected to see my clothes rack and my extra cabinets, but there was a long wooden staircase leading underground, instead. When I saw it, my heart skipped four beats. I don't remember ever having a staircase in my closet. I couldn't see the end of it, it was too dark. Out of curiosity (stupidity), I decided to go down it. Right when I stepped in, the door slammed shut behind me.

It took me about a half hour to reach the bottom. There was dead silence, nothing but the sound of my footsteps. Once I reached the bottom, I looked around and saw nothing but a small, square, grey room that was illuminated by only one flickering lightbulb in the center. There was also an old grey couch, a black armchair, a small wooden coffee table, and an old TV.

I stepped towards the couch when the TV turns itself on. All that was shown was that (X) symbol for about 20 minutes before it disappeared and just showed a completely blurred picture of someone and a muffled voice. I kept watching to see if the quality would get better. Eventually, the picture and the sound did get better, but I don't think I wanted it to.

It was Zach sitting in the woods. He had bags under his eyes, his skin was paler than ever, his nose was bleeding from both nostrils,  as well as his ears. This is what I remember him saying, in a low raspy voice:

"Hey, buddy. It's me, Zach. I just wanted to say I'm sorry for leaving you and my family behind, but mostly you. Haha."

At this point he was smiling, which made me feel a little better.

"I feel really guilty for not showing up to your party, man. I really wanted to go."

He looked down with a sad look on his face and was silent for a few seconds. He looked back into the camera and smiled again.

"I got you a present, though. It's back in my house. I don't remember where, but it's there. I promise. I won't tell you what it is, 'cause I wanted it to be a surprise."

He looked down again and had the same sad look on his face. He gave a really long sigh, but was interrupted with a short gasp as he swung his head around, as if he heard something behind him. He looked back at the camera, terrified.

"Listen to me closely. Stand up."

I didn't even notice I was sitting down in the chair.

"Turn around. And walk down the hallway until you reach the end. Then go up the stairs and don't look back. Ever."

I did what he said. That hallway wasn't there before.

"Your present will help you here on. Good luck, broth--"

His voice was cut out by loud audio distortion and an ear-piercing scream. I wanted to turn around, but I didn't.

I came to the surface and a month had passed, even though I was down there for no longer than an hour. Everything in my room was completely how I left it. Nothing has changed. Even my family didn't realize I was gone. I'm going to Zach's house to investigate soon.

By the way, Jared was killed when I was gone. He went back to the woods.