"Mon ami," he said, turning to me, "somebody stepped on that cup, grinding it to powder, and the reason they did so was either because it contained strychnine or—which is far more serious—because it did not contain strychnine!"
I made no reply. I was bewildered, but I knew that it was no good asking him to explain. In a moment or two he roused himself, and went on with his investigations. He picked up the bunch of keys from the floor, and twirling them round in his fingers finally selected one, very bright and shining, which he tried in the lock of the purple despatch-case. It fitted, and he opened the box, but after a moment's hesitation, closed and relocked it, and slipped the bunch of keys, as well as the key that had originally stood in the lock, into his own pocket.
"I have no autho
