A restless night

It happened in winter, in late January. Left alone at home, I couldn't sleep—insomnia had been keeping me awake for four days now. It seemed I was only getting three or four hours of sleep a night. It was easier when my roommate was awake with me—it was boring being alone. We worked at a gas station and studied at the same time, and the money we earned was enough to cover half the rent and my own expenses.

But that night, the roommate wasn't there, and I tossed and turned in bed, unable to fall asleep again. Finally, I got up, went to the kitchen, made some coffee, and, throwing on a bathrobe, crawled out onto the balcony. While smoking, I became very cold and decided to take a warm shower. But my bathing ritual was interrupted by a persistent knock on the door. As I climbed out of the bath, I shouted, "Just a minute!" and started getting dressed. The knocking continued.  Opening the door, I discovered the light was out in the entryway, and there was no one there.

After blurting out some heartfelt promises of a hard fate to the unknown enemies, I returned to the apartment. But before I could even enter the room, there was another knock. It felt like someone was pounding with both hands. This time, I practically ran out into the hallway, shouting, "Well, that's it, you've had enough!" but again, there was no one there.

This repeated itself a couple more times, then stopped. After reading for a while, I lay down on the bed and finally fell asleep.

In the morning, an agitated neighbor woke me:

"You know, last night, the woman from the third floor was stabbed to death in our building. Well, the one who lived right below us. The worst part is, first they cut her throat, and then they stabbed her about ten times. She stayed alive for half the night, but she couldn't call for help."  They say if someone had found her, they would have saved her... By the way, did you hear anything last night?

"No..." I mumbled, trying to calm the thoughts in my head.

Of course, it could have been a coincidence—but what if I was the one who was supposed to save her? Even now, every thought of that gives me a vague feeling of guilt...