“Interesting problem,” said Ellery dreamily. “I suppose you all saw the significance of the treasure hunt?”
Lieutenant Fiske looked blank. “I guess I’m thick. I don’t.”
“Pshaw! At the time I suggested the game I had no ulterior motive. But when the reports came in, and I deduced that the pearls were in the sunset gun, I saw a way to use the game to trap the thief.” He smiled at Leonie, who grinned back. “Miss Barrett was my accomplice. I asked her privately to start brilliantly — in order to lull suspicion — and slow up as she went along. The mere use of the gun had made me suspect Harkness, who knows guns; I wanted to test him.
“Well, Harkness came through. As Miss Barrett slowed up he forged ahead; and he displayed cleverness in detecting the clue of the ‘greenwood’ tree. He displayed acute observation in spotting the clue of the cigaret. Two rather difficult clues, mind you. Then, at the easiest of all, he becomes puzzled! He didn’t ‘know’ what was meant by the cannon’s mouth! Even Mrs. Nixon — forgive me — spotted that one. Why had Harkness been reluctant to go to the gun? It could only have been because he knew what was in it.”
“But it all seems so unnecessary,” objected the Lieutenant. “If you had the fingerprints, the case was solved. Why the rigmarole?”
Ellery flipped his butt over the parapet. “My boy,” he said, “have you ever played poker?”
“Of course I have.”
Leonie cried: “You fox! Don’t tell me—”
“Bluff,” said Ellery sadly. “Sheer bluff. There weren’t any fingerprints on the can.”