"Why, it's plain enough! I hadn't thought of it. It suddenly occurred to me. It suddenly came to me while you were off to London. Here I had what could solve all our troubles. I put it first here, then there. Everywhere I could. Went on for an hour—all over the room! All over the rug where it dropped. Then one of your guests came in. I didn't want to be seen at it. I was putting it back into my pocket when my hand came close by the side of his coat. Bless my heart! It pointed!"
He leant forward again and tapped his cousin more solemnly still, this time on the chest. "Mark my words! That young man's got it!"
"Which young man?" said Humphrey, remembering what counter accusation the Professor would naturally make, and thinking at once of Galton.
"That young writing fellow," said Cousin Bill. "That newspaper chap McTaggart. McTaggart, McTaggart, McTaggart, McTaggart, McTaggart."
Humphrey de Bohun hesitated. "My dear Bill," he said, "you never know. He might have had something else in his pocket—also crystal, or—I don't know ... something."
The Professor wagged his head with all the dignity of a goat.
"Won't work, Humphrey!" he said. "Won't work! One can always tell the size by the distance. It wasn't some ring or small thing of that kind. Besides which, he wouldn't have such a small thing of his own in his pocket. No, the Emerald's there all right. And I'll tell you something that makes me surer still. I took occasion to brush up against him—there was a hard slab in that pocket, Humphrey. In that pocket. A small, hard slab! Slab! ... Hard slab! ..."
An awful task arose in the conscience of Humphrey de Bohun. He must play the spy again. He must mistrust yet another guest.
But wait! Should he tell the great detective when he arrived? No. It would be only fair to seek the young man first and warn him. But he hesitated and he put it off. He would wait till dinner time, or nearly dinner, when the poor fellow was changing. He would make it quite clear that there would be no consequences—only, he must confess and restore. Then he suddenly thought of what would happen if he drew blank, as he had in the case of the strange being before him. But he was in some agony.