The grave I dug Without knowing Why

"I was in a backyard I didn't recognize, digging a hole with one of those small garden shovels. I don't know why I was digging or what I thought I'd find. The dirt was weirdly easy to move at first, then it got harder, like the ground didn't want me to keep going. At some point I realized I was digging a grave, though I never saw anyone in it. I just knew that's what it was. I kept thinking I should stop, but my hands kept moving. Every time I looked down, the hole seemed deeper than it should've been, like I'd been digging for hours instead of minutes. Then I found a small metal box near the bottom. I couldn't open it. I heard someone behind me say, "You already know what's in it," but when I turned around, nobody was there. I woke up before I could climb out, still feeling dirt under my nails."