Crossing Dimensions

There have always been two dimensions: the good dimension and the evil dimension. They have always lived apart. But then, one day, the dimensions cross.
Now, all of a sudden, there are things happening in the good dimension because of the evil dimension. A young girl sets out on an adventure to stop the evil. She finally gets to who's causing it: but is there more to the story than it seems?

I don't mean to copy anyone else's story. Any instances are purely coincidental.