I was home alone last week when I heard a voice behind me.

“Thank you.”

The little girl’s voice was as plain as day — not something you might imagine in your mind, but something real you would hear with your ears. I had just flushed the upstairs toilet when I heard the voice. I spun around to see who was standing behind me, but no one was there.

Had one of the kids stayed home sick from school? I tip-toed out of the bathroom and looked around. All the lights upstairs were off. I stood still for a long time, waiting to hear it again. I went back to the bathroom and waved my arms around in the air like a madman, thinking maybe I had set off one of the kids’ motion sensitive toys.

Nothing.

After thoroughly searching the upstairs I came downstairs and, with the precision of a one-man SWAT team, searched the rest of the house. If there was a girl or a ghost on the loose, I would find it. I searched each room, my heart skipping a beat as I peeked inside each closet. I’ve watched too many horror movies for this to be any fun.

Finally, I peeked outside through the closed blinds. Susan’s car was gone. I was home, alone.

I will not lie and say that for a few minutes I did not question my own sanity. I was sure I had heard the voice and not imagined it — but then again, wouldn’t a crazy person think the same thing?

I checked the bathroom a few more times that afternoon, investigating the counter for any sign of something that would make noise. There was nothing there.

The solution to my mystery came the following day in the same bathroom. I was home alone (again) and this time I had closed and locked the door behind me in hopes that it would keep the ghost from spying on me. Right after I flushed the toilet, I heard a weird sound — air bubbles trapped in the pipes, I think, but a distinctly familiar sound: “craaa cruuu,” it said.

Or, to someone not expecting it, “thank you.”

“You’re welcome,” I replied, as the water and my ghost spiraled down the drain.