"So you did. That's the way I remember it, too."

"Yes, but there was more to it than that," he said. "I took it back to the table with me and set it down next to my money-so that each time I reached over for some change, I automatically glanced at it. After a time I became aware of a tiny flaw, a little imperfection at the base of one of the limbs. It was quite insignificant, but it irritated me more and more each time that I looked at it. So, when you two left the room later, to bring in more cold beer and sodas, I took it over and switched it with one of those on the shelf."

"I begin to see."

"Okay, okay! I probably shouldn't have done it. I didn't see any harm in it at the time. They were just prototype souvenirs he was fooling with, and the difference wasn't even noticeable unless you were looking hard."

"He'd noticed it the first time around."

"Which was good reason for him to consider them perfect and not be looking again. And what difference did it make, really? Even in the absence of a six-pack the answer seems obvious."

"It sounds all right, I'll give you that. But the fact is that he did check-and it also seems that they were more important than he had indicated. I wonder why?"

"I've been doing a lot of thinking," he said. "The first thing that occurred to me was that the souvenir business was just a story he made up because he wanted to show them off to us and he had to tell us something. Supposing he had been approached by someone from the UN to produce a model-several models-for them? The original is priceless, irreplaceable and on display to the public. To guard against theft or someone with a compulsion and a sledgehammer, it would seem wisest to keep it locked away and put a phony one in the showcase. Paul would be a logical choice for the job. Whenever anyone talks crystallography, his name comes up."