You were out of town for the weekend. When you came back to your apartment, your mailbox was stuffed full. There were at least thirty letters. There were letters with no return address; several of them felt soggy and heavy, as though they were recently wet, or perhaps contained a liquid. All of the letters have your name and address written on them, and many of them had your name scratched all over them in red ink. They don't smell nice; they smell like rotting meat and old garbage, and you're reluctant to take them back to your room, but curiosity gets the better of you. You manage to cart them all back to your room; you dump them in your kitchenette sink because you don't want them smelling up the rest of the apartment.
You grab one that doesn't seem damp and isn't covered with writing, and open it up. There's pictures inside. There are pictures of people you don't know, with their eyes torn out, teeth missing, unhinged jaws hanging open, throats ripped out, etc. You're horrified, and yet you can't help but wonder what's in the rest of the ltters. You open more and more to discover increasingly gruesome photos of dead people. There are piles of bodies with limbs missing, splayed open corpses on operating tables with their vital organs removed, hanged bodies that have been gutted and bled dry. Some of the soggy letters had blood and other fluids in them.
The more letters you open, the more you notice that not all of the people are strangers. Some of them were people you see at work, others people you went to high school with. By the time you get to the last few letters, the pictures are of the mutilated bodies of your close friends and family members.
Eventually, you reach the last letter. You don't want to know what's in it, but it's not like you have a choice now. You peel the letter open, and it's a picture of yourself. You're not dead, your eyes are intact, and you have no limbs missing. It's a picture of you entering your apartment earlier that day, shortly before you collected your disgusting letters.
As you hear a door elsewhere in your apartment, you black out.