All the interviews seemed to blend into one, and they all ended with the same question, in varying forms: Have you recently been to Africa?
About one quarter of the group said yes, including Mrs. Dent, Reverend Vervain, a frog named Gerald Overs, Mr. Boyette and, according to Reverend Vervain, the deceased Miss Smithe.
No one but Mr. Boyette and Miss Blyde seemed to have motive. Everyone else would have had means of slipping something into the punch, the undoubted source of the poison. Poison was the coroner's immediate ruling upon seeing the body.
Mr. Ackerman followed Inspector King into the large parlor where the suspects sat.
"It could be any number of poisons," King muttered.
"No," said Ackerman quietly. "Not any." He reached into his pocket and produced the bottle he had rescued earlier. "Quinine. A fast-acting poison that yields the same symptoms Miss Smithe experienced before her heart failed: paleness, sweating, fainting and fits. It comes together quite nicely, actually."
"Where did you get that bottle?"
"What? This? This is table salt." He handed the bottle over to King and frowned. "The bottle might have once contained quinine; one can not be certain. I merely found it lying by the piano; an interesting clue."
"'Clue?'" King asked. "So, you're saying this 'quonine' stuff in the punch was the one and only murder weapon?"
"'Quinine.' And in answer to your question, 'no and yes.' It was meant to look like the punch has been poisoned, which, in some respects is true. I'm sure that three glasses or more of that stuff would kill any of us."
"But nobody's died so far besides Miss Smithe," said King through gritted teeth.
"Precisely. Which, I think is a very good clue." Ackerman smiled at everyone's bewildered face. "You are perhaps unaware that Miss Smithe was being treated for malaria?"
There were more mutterings and exchanges of glances.
"Quinine," he continued, "is a poison used to treat cases of malaria, a disease—"
"Yes, yes; I'm quite aware of what malaria is. So, she took a dose of quinine at home, came here, drank the punch—"
"Which was laced with quinine."
"Right, that. So you're saying she unwittingly overdosed?"
Ackerman clapped his hands together. "Bravo, Inspector, bravo."
Instead of looking pleased at the praise, Inspector King looked ready to explode. "But how does this fit in with your theory of the X Murders?"
"'X Murders'?" said Miss Blyde. "That's the second time that's been mentioned this evening."
Mrs. Dent gasped. "You don't know? Why, this very house was home to the first X Murder, ten years ago to this day!”
There was a collective shudder.
Looking delighted, Mrs. Dent continued. "He always left his mark somewhere, an X, you know. And there was no rhyme or reason to his killings. No mobile operetta… No, that's not the word, it's—"
Ackerman stepped in. "Oh, there was a modus operandi: He never did the same murder twice, or so he thought. Sometimes it was strangling, sometimes it was stabbing, and, in this case, it was poisoning—though, he has done poisoning before, just not this fast-acting. No, what ties all the murders together is the X mark—"
"But, why, we could be dealing with a copycat!" said Mrs. Dent, deflating slightly.
"—And the Gray threads."
King narrowed his eyes. "Gray threads?"
"Yes, Inspector, you will remember that small strands of gray thread were found on the scene of each crime?"
The inspector looked at him thoughtfully for a moment, and then said, "Yes. But that was never revealed to the public… until your blunder just now."
"Oh, I don't think it really matters any more. The murderer wore gray gloves. The murderer is standing in this very room. The murderer is…I, as a matter of fact."