Large black filmy area in night sky with luminescent clouds. Movement was amoeba-like but it remained in the same spot.I'd gone for a weekend with some of my girlfriends and I'd fallen asleep on the couch for awhile. All but one of my friends had gone to bed. She called me out onto the porch to look at the night sky. It had been a rainy day and cloudy night. It was a dark but still somehow luminescent night of clouds. In the far distance was a slit of fiery glow from the power plant on the other side of Lake Anna. As I looked toward a dark corner of the sky, I noticed a dark wavering before a sea of luminescent clouds. I felt as though I was seeing it track the movement of my friend so I thought it was her shadow. But, I knew it was impossible for that to happen given the lack of light from the correct angle to cast it where it floated. As that understanding was making its way into my conscious understanding, I saw that my friend stood still but the dark wavering kept going. It was an enormous black sheet, filmy, slipping around at its borders the way an amoeba does. When we understood we were seeing something very strange that neither of us had ever seen before, we went in the house and locked the doors. That scared us. We have tried various internet searches and have yet to find anything remotely like it.