I was going outside of my house and everyone that I live with was asleep. When I was closing my door to come outside I clearly heard 3 knocks coming from the inside of the door. But when I opened it there wasn't anyone or anything there. I don't know what it could have been, but it gave me a sinking feeling. So I closed the door and ran to be under the moonlight. It calmed me, now I just don't know.
Can anyone help me understand what this could have been?