I'm no evil spirit.
Harry sighed and put up the most deeply hurt and melancholic expression he could as he said in a low tone. "Mom... I knew I had to tell you this eventually when you noticed the changes, but I did not expect that you'd assume I'm an evil ghost. Let me tell you what happened.
That day in the cart... For some reason, my stomach ached extremely, and before I knew it, I was dead. As soon as I died, it was all flashes of white light as I met grandpa and many of our ancestors, before seeing a large projection of a person that I did not know.
He looked at me with solemn eyes and said in a soothing voice that made all the muddiness in my head go away, 'Oh my dear descendant, do you want to be my messenger?'