Harry Potter and the Multiple McGonogalls

In spite of being a grown adult IRL, in this dream I was an 11 year old Harry Potter trying to get to my first year at Hogwarts.  It was night time with a light drizzle.  I had already been to the dormitory to drop off my belongings, and I was told I needed to get to "Hogwarts" for the evening meal and ceremony.  In this case, I think Hogwarts actually meant the Great Hall.

After leaving the dorm, I was walking through the fairly empty streets of a normal muggle city.  I came to a part that had fewer lights and I could see the night sky pretty clearly, and there were tons of stars out.  I realized I had been instructed to follow the stars in order to make it to the Great Hall, but as I was looking at them, they started moving and swirling around.  Some were small groups that moved around each other, and other stars moved across the canvas of the night sky.

I was starting to feel very frightened, both because I knew the stars were not supposed to move, and also because I was going to be late to the Great Hall, and as I looked around, Professor McGonogall showed up.  She looked up at the sky and said something like, "This won't do," and raised her wand, swirled it around her head once and then flicked it at the sky.

All of the stars moved back to their original positions in about 5 seconds time.  I looked around to say thank you to Professor McGonogall, but she was nowhere to be found.  I didn't think much of it, and I kept walking until I finally got to the Great Hall.

When I walked in, Professor McGonogall came up to me and asked me where I'd been, and I told her about the stars and said, "Wasn't that you that came and helped me?"  She said, "It certainly was not!" and acted very huffy about it.  We quickly came to the conclusion that someone out there was pretending to be her, and that in spite of them helping me, it was someone that was dangerous and it was a very bad thing.  She sped off to go deal with it.

A little while later the dinner and ceremony were done, and I was back at the dorm with Ron.  I was in this spot that almost felt like a stone stairwell, but it was also supposed to be my dorm or bunk.  It was very high up, and there was a window looking out into the moonlit yard to my right. I also had the feeling that the part of the dorm I was in was suspended over open air, like it was hanging off the side of a tower. 

Ron was unpacking, I was telling him about what was going on with the imposter.  He thought it was weird, too.