Knock at the door

I sat in the living room watching "Riverdale" when I heard a knock on the door. I rose up and went to the door to open it. I turned the Bolt to unlock, when I heard whispers. I never thought and wanted the view panel at our door till that day. I wanted to see who it was. I called out "who is it?" but there was no answer. I turned off the TV and went to my room, picked my phone to call my mom and ask where she is. "Hi mom! " I said, "When will you be back? ", she answered on the other end "Soon", and that was the conversation.
I brought out a book to read in order to calm down a bit not because I was in the mood to read, I wanted to go back to watching my movie but I was scared of turning on the TV because of the sound. I opened the middle of the book, it was "Harry Potter and the Chamber of Secrets" it belonged to my 12 year old sister. I was looking at the page and seeing how tiny the font was for me to read when I heard a knock again. I rose up hurriedly like cold water was poured on me. I went to the kitchen, grabbed a knife and went to the door and asked once more "who is it?", there was no answer. I opened the door slowly and I saw no one. There was no sign of any human activity at the front door. Till date I wondered what actually happened that day.