Miss Sutcliffe cried:
“Why, the glass, of course.” She nodded to where the glass lay on the floor as it had fallen from Sir Charles’s hand. “You only put water in, but if it had been nicotine—”
“Let us suppose it was nicotine.” Poirot touched the glass gently with his toe. “You are of opinion that the police would analyse the glass, and that traces of nicotine would be found?”
“Certainly.”
Poirot shook his head gently.
“You are wrong. No nicotine would be found.”
They stared at him.
“You see,” he smiled, “that is not the glass from which Sir Charles drank.” With an apologetic grin he extended a glass from the tail pocket of his coat. “This is the glass he used.”
He went on:
“It is, you see, the simple theory of the conjuring trick. The attention cannot be in two places at once. To do my conjuring trick I need the attention focused elsewhere. Well, there is a moment, a psychological moment. When Sir Charles falls—dead—every eye in the room is on his dead body. Everyone crowds forward to get near him, and no one, no one at all, looks at Hercule Poirot, and in that moment I exchange the glasses and no one sees….
“So you see, I prove my point…There was such a moment at Crow’s Nest, there was such a moment at Melfort Abbey—and so, there was nothing in the cocktail glass and nothing in the port glass….”
Egg cried:
“Who changed them?”
Looking at her, Poirot replied:
“That, we have still to find out….”
“You don’t know?”
Poirot shrugged his shoulders.
Rather uncertainly, the guests made signs of departure. Their manner was a little cold. They felt they had been badly fooled.
With a gesture of the hand, Poirot arrested them.
“One little moment, I pray of you. There is one thing more that I have to say. Tonight, admittedly, we have played the comedy. But the comedy may be played in earnest—it may become a tragedy. Under certain conditions the murderer may strike a third time…I speak now to all of you here present. If anyone of you knows something—something that may bear in any way on this crime, I implore that person to speak now. To keep knowledge to oneself at this juncture may be dangerous—so dangerous that death may be the result of silence. Therefore I beg again—if anyone knows anything, let that person speak now….”
It seemed to Sir Charles that Poirot’s appeal was addressed especially to Miss Wills. If so, it had no result. Nobody spoke or answered.
Poirot sighed. His hand fell.
“Be it so, then. I have given warning. I can do no more. Remember, to keep silence is dangerous….”
But still nobody spoke.
Awkwardly the guests departed.
Egg, Sir Charles and Mr. Satterthwaite were left.
Egg had not yet forgiven Poirot. She sat very still, her cheeks flushed and her eyes angry. She wouldn’t look at Sir Charles.
“That was a damned clever bit of work, Poirot,” said Sir Charles appreciatively.
“Amazing,” said Mr. Satterthwaite with a chuckle. “I wouldn’t have believed that I wouldn’t have seen you do that exchange.”
“That is why,” said Poirot, “I could take no one into any confidence. The experiment could only be fair this way.”