One night, we were sitting in the living-room, watching television.

“Joe,” she asked me, “did you dust the den?”

“Dust the den? What would I want to do that for?”

“Well, someone did. Maybe it was Bill.”

“Bill wouldn’t be caught dead with a dustdoth in his mitt.”

“I can’t understand it, Joe,” she said. “I went in there to dust it and it was absolutely dean. Everything just shone.”

Sgt. Friday was trying to get the facts out of someone and his sidekick was complaining about some relatives that had come to visit and I didn’t pay much attention at the time.

But the next day, I got to thinking about it and I couldn’t get it off my mind. I certainly hadn’t dusted the den and it was a cinch Bill hadn’t, yet someone had if Helen was ready to admit it was clean.

So, that evening, I went out into the street with a pail and shovelled up a pailful of dirt and brought it in the house.

Helen caught me as I was coming in the door. “What do you think you’re doing with that?”

“Experimenting,” I told her.

“Do it in the garage.”

“It isn’t possible,” I argued. “I have to find out who’s been dusting the den.”

I knew that, if my hunch failed, I’d have a lot to answer for when she followed me and stood in the doorway, ready to pounce.

There was a bunch of junk from the Trader standing on the desk and a lot more of it in one corner. I cleared off the desk and that was when Bill came in.

“What you doing, Dad?” he asked.

“Your father’s gone insane,” Helen explained quietly.

They stood there, watching me, while I took a handful of dirt and sprinkled it on the desk top.

It stayed there for just an instant—and then it was gone. The top of the desk was spotless.

“Bill,” I said, “take one of those gadgets out to the garage.”