He searched their faces deliberately. The Inspector leaned against the wall, watching with bright eyes.
“No suggestions? It’s quite outré, as I’ve said. Well, examine it point by point. The ‘knave’ element first. A curious coincidence, but scarcely more than that. Certainly a murderer may be termed a knave, but that scarcely helps any one but the panting collector of classic understatements. The fact that ‘knave’ is commonly called ‘jack’? There is no Jack in our little company; the only one to whom it might have applied, John Xavier, having himself been the first victim. Well, then, how about the suit-symbol — the diamond? There’s no question of gems involved; the only possible connection here would be—” he paused, “the rings that seem to have been stolen. But none of these was a diamond ring. On the surface, then, no indication of what the meaning might be.” And then he whirled so unexpectedly upon Mrs. Carreau that she shrank back in her chair. “Mrs. Carreau, what does the word carreau mean in English?”
“Carreau?” Her eyes became enormous brown pools. “Why” — her eyes flickered — “it means so many things, Mr. Queen. A hassock, and a tailor’s goose, and a lozenge, and a pane of glass...”
“And a ground floor, and a certain kind of tile. Quite so.” Ellery smiled coldly. “There’s also a very significant idiom: rester sur le carreau, which may be translated to: to be killed on the spot, a singularly felicitous French version of our Chicagoese expression... all of which however we may discount as irrelevant.” He continued to eye her steadily. “But what else does carreau mean?”
Her eyes fell. “I’m afraid — I don’t know, Mr. Queen.”
“And the French so sportively inclined! Have you forgotten that in French the word ‘diamond’ as applied to playing cards is carreau?”
She was silent. Each face mirrored amazement and horror.
“But, good lord,” breathed Dr. Holmes. “That’s insane, Mr. Queen!”
Ellery shrugged without removing his fixed glance from the shrinking woman. “I’m recounting facts, not fancies, Doctor. Doesn’t it strike you as enormously significant that the fatal card is a diamond, that ‘diamond’ is carreau in French, and that we have several Carreaus in this house?”
Miss Forrest jumped from her chair and advanced with white lips upon Ellery. “I have never heard such unmitigated and cruel nonsense in my whole life, Mr. Queen! Do you realize what you’re insinuating on the basis of such — such flimsy evidence?”
“Sit down, please,” said Ellery wearily. “I realize a good deal more, I think, my loyal lady, than you do. Well, Mrs. Carreau?”
Her hands were twisting like snakes. “What do you expect me to say? All I can say is that — you’re making a terrible mistake, Mr. Queen.”
The twins leaped from the sofa. “You take that back!” cried Francis, doubling his fists. “You can’t s-say things like that about our mother!”
Julian shouted: “You’re crazy, that’s what you are!”
“Sit down, boys,” said the Inspector quietly from the wall.
They glared at Ellery, but obeyed.
“Let me continue, please,” said Ellery again in a tired voice. “I don’t relish this any more than the rest of you. The word ‘diamond’ in the card sense is, as I’ve pointed out, carreau. Is there anything in our facts which bolsters this admittedly fantastic theory that a Carreau, so to speak, was designated by John and Mark Xavier when they left the jack of diamonds as clues to their murderer? Unfortunately there is.” He waved his hand and repeated: “Unfortunately — there is.”
From the wall came the Inspector’s voice, calm and impersonal. “Which one of you boys,” he said clearly to the Siamese twins, “killed those two men?”
Mrs. Carreau sprang to her feet and bounded across the intervening space like a tigress. She stood before the speechless boys, her arms outspread, her whole body vibrating with passion. “This has gone far enough!” she cried. “I think even you stupid men must see the absurdity of accusing these — these children of murder. My sons murderers! You’re mad, both of you!”
“Absurdity?” Ellery sighed. “Please, Mrs. Carreau. You’ve evidently failed to grasp the significance of the clue. That card was not only a diamond, but a jack of diamonds. What is the appearance of the knave card? It represents two joined young men.” Her mouth came open. “Ah, I see you’re not quite so certain of its absurdity. Two joined young men — not old men, mind you, for a king would have sufficed for that — but young men. Joined! Incredible? I told you it was. But we have two joined young men in this house, and they are named Carreau, you see. What is one to think?”
She sank onto the sofa beside the boys, unable to speak. Their young mouths were working soundlessly.
“Moreover, we ask the question: why was the card torn in half in both instances, leaving — so to speak — only one of the two joined men as a clue?” Ellery continued with weary inexorability. “Obviously because the dead men intended to show that one, not both, of the Carreau twins was the murderer. How could this be? Well, if one was dominated by the other, was compelled to be present against his will because of sheer physical inability to hang back, was a mere bystander while the other committed the actual crimes... Which of you shot Dr. Xavier and poisoned Mark Xavier, boys?”
Their lips quivered; the fight had quite gone out of them. Francis whispered in a voice close to tears: “But... but we didn’t, Mr. Queen. We didn’t. Why, we... we couldn’t do... that. We just couldn’t. And why should we? Why? It’s so... Oh, don’t you see?”
Julian shuddered. His eyes were fixed on Ellery’s face with a sort of fascinated horror.
“I’ll tell you why,” said the Inspector slowly. “Dr. Xavier was experimenting with Siamese-twin animals in his laboratory. You people had some notion when you came up here that the doctor could perform a miracle, could separate the boys surgically—”
“That’s nonsense,” muttered Dr. Holmes. “I’ve never believed—”
“Exactly. You’ve never believed it could be done, Holmes. It’s never been done successfully, has it, with twins of this type? So I say that it was you who threw the monkey-wrench into the works; you went on record as not ‘believing,’ you made these people doubt the ability of Dr. Xavier. You talked to the twins, to Mrs. Carreau, about it, didn’t you?”
“Well...” The Englishman was writhing. “Perhaps I did advise them that it was a very dangerous experiment—”
“I thought so. And then something happened.” The Inspector’s eyes were bright marbles. “I don’t know what, exactly. Maybe Dr. Xavier was stubborn, or insisted on going ahead. The boys, Mrs. Carreau, got frightened. It was a murder in self-defense, in a way—”
“Oh, don’t you see how ridiculous that is?” cried Miss Forrest. “How childish? There was nothing Machiavellian about Dr. Xavier. He wasn’t the ‘mad scientist’ of the thrillers and movies. He wouldn’t have gone ahead with such an operation without the full consent of all parties concerned. Besides, what was to prevent us from just leaving? Don’t you see? It simply won’t stand examination, Inspector!” Her voice rang with triumph.
“Besides,” snapped Dr. Holmes, “there was no certainty at all about the surgery. Mrs. Carreau brought the boys up here for observation only. Even had everything been otherwise settled, an operation here would have been impossible. But then Xavier’s experiments on animals were a matter of pure research, antedating Mrs. Carreau’s arrival. I assure you that Dr. Xavier never had anything in mind concerning these lads, Inspector, other than mere theory. This is all very shockerish, Inspector.”