“There might be a reason for that,” said Japp. “Do you know that just beyond the lake, a little gate leads out on to the hill, and not three minutes’ walk brings you to⁠—what do you think?⁠—a lime kiln .”

“Good heavens!” I cried. “You mean that the lime which destroyed the body would be powerless to affect the metal of the ring?”

“Exactly.”

“It seems to me,” I said, “that that explains everything. What a horrible crime!”

By common consent we both turned and looked at Poirot. He seemed lost in reflection, his brow knitted, as though with some supreme mental effort. I felt that at last his keen intellect was asserting itself. What would his first words be? We were not long left in doubt. With a sigh, the tension of his attitude relaxed, and turning to Japp, he asked: