the difference between nightmare and memory

What I just had was both.
I chanted for a while (‘I want to remember’) and then my mind wandered. I had visions of what happened in that time that I can’t remember.
I did some freakish things. Disturbing, perverted things. The visions connect the dots, but in such a messed-up way that I get really scared just thinking about it. No way am I typing them here.
Maybe those visions were just my imagination. But I have a way to check. I saw things at the school in the vision, parts of the school I’ve never seen before. I’ve got details branded into my memory.I’ll go to school tomorrow, and those details won’t be there, and I’ll just chalk it up to a bad trip or something. And I’ll never go down to the basement again.