“One of the world’s greatest what? Say it again.”

“He knows more about poisons than almost anybody,” I explained. “Well, my idea is, that perhaps he’s found some way of making strychnine tasteless. Or it may not have been strychnine at all, but some obscure drug no one has ever heard of, which produces much the same symptoms.”

“H’m, yes, that might be,” said John. “But look here, how could he have got at the coco? That wasn’t downstairs?”

“No, it wasn’t,” I admitted reluctantly.

And then, suddenly,

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