So, when I found a yellow Post-it note on my desk, written in wobbly handwriting I didn’t recognize, I didn’t think too much of it. It reminded me to pick up cucumbers and crackers, and mail a letter. Things I had considered doing but hadn’t told anyone about. It sat right in the middle of my desk like a message from a ghost.

I checked my phone, wondering if I’d left myself a reminder and forgot. Nothing. Maybe I scribbled it down half-asleep? Maybe my brain was messing with me.

Then I tossed the note in the trash and moved on.

A few days later, another note appeared. Same handwriting. Same yellow Post-it.

Make sure you save your documents.

Now, that was a little unsettling.

I was a freelance writer, working on a big project the night before. The message felt oddly relevant. But I lived alone. My doors were locked. No signs of a break-in. No missing items. Just the note.

I convinced myself it was stress. Too much work, not enough sleep. I crumpled it up and threw it away.

Then, one night, something woke me up. I wasn’t sure what. Maybe the silence, maybe a shift in the air. When I turned on the lamp, another note sat on my bedside table.

Our landlord isn’t letting me talk to you, but it’s important that we do.

My breath caught in my throat. The room suddenly felt wrong.

Who was writing these notes? And why was my landlord involved?

I tore through my apartment, checking the locks, the windows. Nothing. My landlord had a key, but we only scheduled visits for repairs. He wouldn’t just show up. Would he?

Then I remembered—the webcam. After the first note, I had set up an old webcam on my desk, using a security cam app to record any motion.

I scrambled to check the footage. The files were gone. Not just missing—deleted.

My stomach twisted. I hadn’t touched them. Someone had noticed the camera, accessed my laptop, and erased the evidence.

My hands shook as I double-checked everything. The recycle bin? Empty. I grabbed a kitchen knife, double-locked my doors, and sat in bed, heart pounding.

The next day, when I returned from the gym, there was another Post-it. But this time, it was different.

It was blank.

It was stuck to the outside of my apartment door.

A cold dread crawled up my spine. Was this a warning? A message? Someone knew I had noticed the notes. Someone knew I wasn’t home.

As I turned, my breath hitched. Other doors in the building had them too.

Different colors—pink, blue, yellow—but all blank.

I didn’t wait to find out what it meant. I grabbed my keys and bolted.

Jessica opened her front door, rubbing her eyes. “Mila? It’s late. What’s going on?”

I pushed past her, pacing. “I need you to tell me I’m not crazy.”

She yawned. “Okay, but if this is about aliens again, I swear—”

“Jess, this is worse. I think someone’s been in my apartment.”

That woke her up. She sat up, listening as I told her everything—the Post-it notes, the deleted footage, the blank note on my door.

When I finished, she exhaled. “Mila, have you checked for carbon monoxide?”

“What?” I blinked.

“CO poisoning. It can cause memory loss, paranoia. What if you’re writing the notes yourself and just… forgetting?”

I wanted to argue, but the thought gnawed at me. I’d been feeling off—waking up with headaches, struggling to focus, feeling exhausted no matter how much I slept.

I left Jessica’s and drove to a gas station. “Carbon monoxide detector, please,” I asked the cashier.

Back at my apartment, I plugged it in.

The number shot up immediately. 100 ppm.

A wave of dizziness hit me. The air felt heavy, pressing down on me. I grabbed my bag, yanked open the door, and stumbled into the hallway, gasping for fresh air.

“Jess,” I said when she picked up the phone. “You were right. The reading is insane.”

“Get outside! I’m coming now.”

The doctor in the hospital flipped through my chart. “You’re lucky you caught this when you did, Mila. Prolonged exposure could have caused permanent cognitive damage. Eventually, you might have lost consciousness and never woken up.”

Jessica squeezed my hand. “You’re okay now. That’s what matters.”

I called my landlord the next day. He wasn’t surprised. Not even a little.

“We’ll get it checked,” he muttered, hanging up. That didn’t sit right with me, so I called the city inspector myself.

That’s when I learned the real nightmare.

The leak wasn’t just in my apartment. It was coming from the parking garage beneath the building.

And my unit? Directly above it.

I had been breathing in carbon monoxide seeping up from below, trapped in my apartment like a slow-motion death sentence.

When I confronted Greg, my landlord, he barely reacted. “You should move out if you’re concerned.”

“You knew,” I accused. “How long has the leak been there? How many tenants have complained?”

He didn’t answer.

Then I remembered the blank Post-it notes on other doors. Just a coincidence? Or a warning?

I moved in with my cousin across town. The inspector reached out to my neighbors, but apparently, my apartment had been hit the worst.

Now that I’m safe, I keep thinking about what would have happened if I hadn’t told Jessica. If I had dismissed it all as paranoia.

But the worst part?

I still don’t know why I wrote that third note.

Our landlord isn’t letting me talk to you, but it’s important that we do.

Was it my subconscious trying to warn me? A desperate part of my brain screaming for help?

Or was someone—something—else trying to get my attention?

I don’t have answers. But I do have one piece of advice:

If weird things start happening, don’t ignore them. Because sometimes, paranoia isn’t paranoia at all.

Sometimes, it’s survival.