“He said twice: ‘That alters everything.’ And I’ve been thinking. You know Inglethorp said he had put down the coffee in the hall? Well, it was just then that Bauerstein arrived. Isn’t it possible that, as Inglethorp brought him through the hall, the doctor dropped something into the coffee in passing?”

“H’m,” said John. “It would have been very risky.”

“Yes, but it was possible.”

“And then, how could he know it was her coffee? No, old fellow, I don’t think that will wash.”

But I had remembered something else.

“You’re quite right. That wasn’t how it was done. Listen.” And I then told him of the cocoa sample which Poirot had taken to be analysed.

John interrupted just as I had done.

“But, look here, Bauerstein had had it analysed already?”