“Just poke the fire!” he said to Euan.
From a drawer in the table he produced a board on which he pinned down the letter with a drawing-pin at each corner. Then he dipped a paint-brush into one of the bottles and carefully painted the whole surface of the sheet with some invisible fluid.
“So!” he said, “we’ll leave that to dry and see if we can find out any little secrets, eh? That little tray’ll do the trick if there’s any monkey business to this letter of yours, Miss Trevert. That’ll do the trick, eh, what?”
He paced the room as he talked, not waiting for an answer, but running on as though he were soliloquizing. Presently he turned and swooped down on the board.
“Nothing,” he ejaculated. “Now for the acids!”
With a little piece of sponge he carefully wiped the surface of the letter and painted it again with a substance from another bottle.
“Just hold that to the fire, would you, Euan?” he said, and gave MacTavish the board. He resumed his pacing, but this time he hummed in the most unmelodious voice imaginable:
She was bright as a butterfly, as fair as a queen,
Was pretty little Polly Perkins, of Paddington Green.
“It’s dry!”
MacTavish’s voice broke in upon the pacing and the discordant song.