There was always a quiet man who lived across the hall from me. He never spoke to anyone. I hardly ever saw him leave his apartment, and whenever I did, he avoided eye contact and hurried inside. My boyfriend used to joke that the man was a spy, always watching us. I would laugh it off, because the idea sounded ridiculous.

After my boyfriend and I broke up, I noticed something unusual. He started visiting that same apartment — often. I would see him knocking softly, then slipping inside as if he didn’t want anyone to notice. I assumed they were friends and brushed it off at first, but the visits kept happening, sometimes late at night.

Then one afternoon, I came home and saw the door across the hall slightly open. It was the first time I had ever seen it unlocked. I hesitated, but curiosity got the better of me. I gently pushed the door open and stepped inside.

The apartment was unnaturally spotless. There was no furniture except a small table with a laptop on it. No pictures, no personal items, not even a jacket or shoes by the door. The place felt empty, like no one truly lived there.

Then I noticed the walls. They were covered with boards filled with papers and photographs connected with red string. My breath caught in my throat when I realized one of the photographs was of me.

Before I could move, the door closed behind me. My ex stood there, watching me quietly.

“I told you he was a spy,” he said. “I just never told you I was one too.”