"It WAS quite blank before I handed it to you--but not now.

I noticed yesterday that your hands were generally moist.

I am sure they are more so now--excitement, you know.

Carruthers, see that he doesn't interrupt." From a drawer, Jimmie Dale took out a little black bottle, the notebook he had used the day before, and the photograph Carruthers had sent him.
On the sheet of paper Clayton had just handled, Jimmie Dale sprinkled a little powder from the bottle.
"Lampblack," explained Jimmie Dale.

He shook the paper carefully, allowing the loose powder to fall on the desk blotter--and held out the sheet toward Clayton.