Her Next Door Neighbor Ep. 1: The Midnight Knock on Room 404

"Knock, knock." At precisely midnight, the heavy knocking sound emanated from within the wall, each strike clearer and more frantic than the last. I clutched my blanket tightly, shrinking into the corner of the bed, too scared to move. This was the seventh day since I moved into this cheap rented room, and the seventh night this sound had tormented me. There is no Room 404 here; the room next to mine, 403, is directly adjacent to 405. When I asked the landlord, he evasively said it was just the expansion and contraction of old water pipes. But I was certain it was the sound of human knuckles striking wood. Even stranger, every time the knocking started, a faint chill would seep from the wall connecting to the next room, accompanied by a faint, rotten-meat-like odor. Tonight, I finally couldn't take it anymore. Grabbing the self-defense baton I kept, I strode to the cold wall. When the knocking began again, I took a deep breath, clenched my fist, and knocked back three times on the wall. "Who's in there!" I yelled. The sound from next door instantly ceased. The entire room was so silent I could only hear my own heartbeat. Just as I thought the other party was scared off and I could relax, my phone suddenly vibrated. It was a text message from an unknown number, containing just one line: "Thank you for opening the door, I'm coming in." At that very second, the door of the closet behind me slowly creaked open from the inside.