The fluorescent lights flickered dimly in the underground subway station as Agent Chen adjusted his worn leather jacket, scanning the late-night crowd. His contact was supposed to meet him here, at this cheap sandwich shop tucked away in a grimy corner. The sign above read “Lucky’s Sandwiches - $2.99” in faded characters.

“The usual, Mr. Chen?” The elderly shopkeeper’s raspy voice carried a hint of recognition. Their eyes met briefly - too briefly.

“Yes. Turkey on rye. Extra mustard.” The coded phrase felt bitter on his tongue.

While preparing the sandwich, the old man’s hands trembled slightly. “Strange times we’re living in. Just yesterday, a woman ordered the exact same thing. Looked a bit like you around the eyes.”

Chen’s pulse quickened. His sister had been missing for three weeks. “Did she leave a message?”

“Check under the wrapper when you’re alone,” the old man whispered, sliding the sandwich across the counter. “And Mr. Chen? Watch the shadows. They’ve been… moving lately.”

The paper wrapper felt unusually heavy. Chen paid and found a secluded bench near the end of the platform. As he unwrapped the sandwich, a small microfilm negative fell into his lap. But something else caught his attention - dark stains on the bread that couldn’t be sauce.

His phone buzzed. Unknown number.

“Did you get my gift, little brother?” His sister’s voice, but different - hollow, almost mechanical. “I’m sorry it had to be this way. They’re watching me now. Always watching.”

“Where are you? What happened?”

“The walls have eyes here, Chen. They… change people. I’m not sure I’m still me anymore.” A pause. “Don’t trust the sandwich shop. Don’t trust anyone with—” The line went dead.

Chen looked up. The old shopkeeper was staring at him from behind the counter, but something was wrong. In the flickering lights, his face seemed to ripple and shift, like wax melting under heat.

The station’s speakers crackled to life: “Last train departing in five minutes.”

Chen stood, his hands shaking. The microfilm felt like it was burning through his pocket. Around him, the late-night passengers had all turned to face him, their features indistinct in the poor lighting.

“You should have ordered the chicken sandwich instead,” the old man called out, his voice now a chorus of whispers. “She did.”

The lights flickered again. In that brief moment of darkness, Chen could have sworn he saw his sister’s face among the crowd - or what was left of it.

The train approached the station, its headlights cutting through the gloom like searchlights. Chen had to make a choice: board the train with the microfilm and whatever terrible truth it contained, or stay and find out what really happened to his sister.

Behind him, the sound of footsteps grew closer.

The train doors opened with a hiss.