"You take 'em. Look 'em over as much as you like. See if you can find anything wrong with 'em… All right. Now shuffle 'em. Shuffle 'em all you want." He waited. "Now spread 'em out on the table. You're doing this trick, not me. Take any card you like. Look at it — don't let me see it. All right. Now, I haven't touched the cards at all, have I, except to give 'em to you? You shuffled 'em and you picked a card without me helping you. I couldn't have forced it on you or anything. Eh? All right. Well, I could put any trimmings I wanted on this trick — any fancy stunts I could think up to make it look more mysterious. They'd all be easy because I know what card you've got all the time. You've got the six of diamonds."
Simon turned the card over. It was the six of diamonds.
"How's that?" Naskill demanded gleefully.
The Saint grinned. He drew a handful of cards towards him, face downwards as they lay, and pored over the backs for two or three minutes before he sat back again with a rueful shrug.
Mr. Naskill chortled.
"There's nothing wrong with your eyes," he said. "You could go over 'em with a microscope and not find anything. All the same, I'll tell you what you've got. The king of spades, the two of spades, the ten of hearts—"
"I'll take your word for it," said the Saint resignedly. "But how on earth do you do it?"
Naskill glowed delightedly.
"Look," he said.
He took off his glasses and passed them over. Under the flat lenses Simon could see the notations clearly printed in the corners of each card — KS, 2S, 10H. They vanished as soon as he moved the glasses and it was impossible to find a trace of them with the naked eye.