When I first moved into my apartment, the landlord told me a strange thing. "Always check that the room is the right one before entering." Sage advice from a master of the obvious, you might say. Truth be told, I hadn't really been paying much attention up to that point.

My landlord was the type of women that put no effort in sounding happy to meet to you, and whatever eastern European accent she had certainly didn't make it any easier to understand. I probably should have asked a few more questions but signing a lease wasn't a process I wanted to prolong any longer than I had to.

Besides, it's not like I really needed an explanation. My early childhood diet didn't consist exclusively of paint chips after all.

For how cheap the rent was, I wasn't about to worry over a bad joke. The place was one of those oddities of design that seemed to suck the fun out of everything anyway. Nothing but a series of copy-and-paste apartments stacked on top of each other for thirteen laborious floors.

Each one was practically identical, right down to the way the front door stuck when it rained. Not a single window among them. They even came furnished with a full set of drab appliances and furniture, devoid of any particular style or taste. It's like living in a filing cabinet.

Sterile and lacking a life of its own. You'd think we all lived in alphabetical order and referred to each other by apartment numbers. My accountant would love this place.

As dull as the accommodations were, it didn't take more than a month for things to get interesting.They were little things at first. Mostly just noises. Nothing particularly sinister but they did a great job of keeping me up at night.

One night I'd hear unintelligible whispers coming from my neighbor's bathroom that lasted for hours, the next I'd swear I heard far off wolf-like howls from the floor above despite a rigidly enforced 'No Pets' policy. Once I even caught the unmistakable sound of crashing waves on sandy beach from an apartment on the sixth floor.

Occasionally, I would hear the noises coming from rooms in my own apartment. However, nothing would be out of place when I checked. I may have forgotten to mention that I live alone.

It took a bit longer for anything really strange to happen though. It was four months into my stay when the sound of clinking glass and slamming cabinets woke me. It came from the kitchen and I knew it had to be an intruder.

I quietly slipped out of bed and grabbed the aluminum baseball bat I keep next to the door to remind me how I really should get more exercise. I must've looked absolutely ridiculous tip-toeing down my carpeted hallway to the kitchen with how much noise the intruder was making. When I reached the doorway to my kitchen, I chanced a peek inside.

Sure enough, I saw a dark figure furiously rooting through my kitchen cabinets. Tightening my grip on the baseball bat, I flipped on the light switch. Lucky thing I did, too. Otherwise, I might have beaten an innocent old woman to death.

My midnight intruder started at the sight of me, her wrinkled face twisting into a mixture of fright and confusion. The unassuming dirty dressing gown and fluffy pink slippers she wore seemed an odd choice for a burglar. I recognized the woman. She was the old lady who lived two doors down from me. I'd even helped her with her groceries that very evening.

After managing to calm the poor woman down and assuring her that she was not in fact in her own flat, my elderly neighbor apologized profusely. She'd woken up in the middle of the night craving a cup, she explained, and must have gotten lost in the dark, unlit building.

How she managed to slip into my apartment without either of us noticing was beyond me. She must suffer from dementia because she was absolutely convinced that she should still be in her own. I don't think she understood just how close she came to a baseball bat to the head and I wasn't in the mood to explain it to her.

I tried to be as polite and understanding as I could as I escorted her back to her apartment, but something was bothering me. Something about the whole affair made the little hairs on the back of my neck stand up.

It wasn't until I locked my front door behind me that I realized what it was. Before going to bed, I remember quite clearly locking the door from the inside. I racked my brain all night but I just couldn't explain how the old woman could've wandered into my apartment without opening my front door. Having no one else to ask, I decided to bring the subject up to my next door neighbor the next day.

Cornering him in the hallway that evening, I had trouble broaching the subject. When I'd finally stammered out my story, however, he seemed rather unsurprised by the whole ordeal. Apparently, this sort of thing happened all the time. Not just to the old lady down the hall either.

Almost everyone in the building had a similar tale. It was the doors, he said. They didn't always lead to the same place. Sometimes, you would be facing a door that led to your bathroom, only for it to lead to your bedroom instead. It could even lead to a completely different apartment on a completely different floor. Once, he heard that someone's closet door had once opened to the alley on the north side of the building.

It was a pretty crazy thing to think your door could lead anywhere in the building without notice but my neighbor seemed to believe that the phenomenon stretched farther than that.

To get around this little nuisance, he suggested I do what the other tenants do. The generally accepted method was to make two marks on either side of each doorway in the apartment with a marker.

That way you could tell if the room you were about to enter was the right one at a glance. If the two marks didn't match up, you were staring at a doorway to the unknown. At least, that was the idea. The old lady must've forgotten to check when she stepped into my kitchen, or at least not seen it in the dark.

My neighbor seemed rather annoyed by the thought. He made it painfully clear that I wait for the door to go back to normal before using it. I should, under no circumstances, ever enter a room that shouldn't be there. Always check first.

My neighbor experienced the anomaly himself in the past but only as a mild annoyance. Even still, he was very adamant that I take the matter seriously. But how could I? Who in their right mind would believe a story as insane as this?

Sure, it could explain how the old lady down the hall got into my apartment without using the front door, but it created all sorts of other questions. And the last thing I wanted to question were the laws of physics. Mass hysteria, it had to be. A building filled to bursting with lunatics.

In the end, I found it simpler to write my neighbor off as a head case and move on with my life. However, I did as he suggested. With a red sharpie secretly "borrowed" from work, I drew a line on each side of every door jamb in my apartment.

It was more out of curiosity than anything else. Or maybe I was just daring the universe to prove me wrong. Either way, after a few weeks, I'd gotten into the habit of checking if both marks were there before I entered a room. I saw it as a little inside joke. When in Rome, do as the whackos do. Eventually, it became a silly little ritual I would do to remind myself the world wasn't crazy. Just the guy next door.

I'd been living in my apartment for a little over a year before it happened to me again. I'd gotten up in the middle of the night to grumpily use the bathroom like I'd done many times before. I was on autopilot. On my way back to bed, I lifted my tired eyes to the doorway leading to the bedroom and grinned at the now familiar red.

But I hesitated. There was only one mark. Though only lit by a small lamp in the hallway, I was absolutely sure there was no red mark on the bedroom side of my door. I stood there for a while blinking sleep from my eyes and trying to stare the second mark back into existence.

The bedroom looked the same as I'd left it minutes before, save for the missing mark on the doorway. Were my eyes playing tricks on me? Maybe I was dreaming. Or was my kooky neighbor's story the real deal? As ridiculous as it sounded, I was sure of one thing. There had been two marks on my trip to the bathroom.

I didn't go in right away. I wanted to, but a small part of me took what my neighbor told me seriously. First, I waved an empty hand in the doorway. Nothing particularly spooky happened.

Emboldened by the knowledge that this phantom room wouldn't immediately melt my skin off, I took a tentative step inside. At first glance, nothing looked out of the ordinary. Everything was where I remember leaving it. Even my comforter was thrown aside like I'd just been sleeping under it minutes before.

But then why was the mark missing from my doorframe? I was certain there had to be something different about this room. In that moment, my neighbor didn't seem so crazy, and all I needed to prove it was to find what was wrong with this room. I tore open my closet and flipped my mattress in search of clues.

Every drawer was emptied on the floor in my quest. I even tore the carpets up at the ends to look underneath. I looked everywhere in my madness but found nothing. Everything was where it should be. Somehow, though, I knew this was not my bedroom and it wasn't until I turned back to the door to check if the second mark was really missing that I realized what was different about it.

This room had no doors.