man of science had picked up the peculiar dagger-sword from the carpet and was examining it intently as he answered:
"Because you find Mr. Todhunter tied up," he said, "you all jump to the conclusion that Mr. Glass had tied him up; and then, I suppose, escaped. There are four objections to this: First, why should a gentleman so dressy as our friend Glass leave his hat behind him, if he left of his own free will? Second," he continued, moving towards the window, "this is the only exit, and it is locked on the inside. Third, this blade here has a tiny touch of blood at the point, but there is no wound on Mr. Todhunter. Mr. Glass took that wound away with him, dead or alive. Add to all this primary probability. It is much more likely that the blackmailed person would try to kill his incubus, rather than that the blackmailer would try to kill the goose that lays his golden egg. There, I think, we have a pretty complete story."
"But the ropes?" inquired the priest, whose eyes had remained open with a rather vacant admiration.
"Ah, the ropes," said the expert with a singular intonation. "Miss MacNab very much wanted to know why I did not set Mr. Todhunter free from his ropes. Well, I will tell her. I did not do it because Mr. Todhunter can set himself free from them at any minute he chooses."
"What?" cried the audience on quite different notes of astonishment.
"I have looked at all the knots on Mr. Todhunter," reiterated Hood quietly. "I happen to know something about knots; they are quite a branch of criminal science. Every one of those knots he has made himself and could loosen himself; not one of them would have been made by an enemy really trying to pinion him. The whole of this affair of the ropes is a clever fake, to make us think him the victim of the struggle instead of the wretched Glass, whose corpse may be hidden in the garden or stuffed up the chimney."
There was a rather depressed silence; the room was darkening, the sea-blighted boughs of the garden trees looked leaner and blacker than ever, yet they seemed to have come nearer to the window. One could almost fancy they were sea-monsters like krakens or cuttlefish, writhing polypi who had crawled up from the sea to see the end of this tragedy, even as he, the villain and victim of it, the terrible man in the tall hat, had once crawled up from the sea. For the whole air was dense with the morbidity of blackmail, which is the most morbid of human things, because it is a crime concealing a crime; a black plaster on a blacker wound.
The face of the little Catholic priest, which was commonly complacent and even comic, had suddenly become knotted with a curious frown. It was not the blank curiosity of his first innocence. It was rather that creative curiosity which comes when a man has the beginnings of an idea. "Say it again, please," he said in a simple, bothered manner; "do you mean that Todhunter can tie himself up all alone and untie himself all alone?"
"That is what I mean," said the doctor.
"Jerusalem!" ejaculated Brown suddenly, "I wonder if it could possibly be that!"
He scuttled across the room rather like a rabbit, and peered with quite a new impulsiveness into the partially-covered face of the captive. Then he turned his own rather fatuous face to the company. "Yes, that's it!" he cried in a certain excitement. "Can't you see it in the man's face? Why, look at his eyes!"
Both the Professor and the girl followed the direction of his glance. And though the broad black scarf completely masked the lower half of Todhunter's visage, they did grow conscious of something struggling and intense about the upper part of it.
"His eyes do look queer," cried the young woman, strongly moved. "You brutes; I believe it's hurting him!"
"Not that, I think," said Dr. Hood; "the eyes have certainly a singular expression. But I should interpret those transverse wrinkles as expressing rather such slight psychological abnormality—"
"Oh, bosh!" cried Father Brown: "can't you see he's laughing?"
"Laughing!" repeated the doctor, with a start; "but what on earth can he be laughing at?"
"Well," replied the Reverend Brown apologetically, "not to put too fine a point on it, I think he is laughing at you. And indeed, I'm a little inclined to laugh at myself, now I know about it."
"Now you know about what?" asked Hood, in some exasperation.
"Now I know," replied the priest, "the profession of Mr. Todhunter."
He shuffled about the room, looking at one object after another with what seemed to be a vacant stare, and then invariably bursting into an equally vacant laugh, a highly irritating process for those who had to watch it. He laughed very much over the hat, still more uproariously over the broken glass, but the blood on the sword point sent him into mortal convulsions of amusement. Then he turned to the fuming specialist.
"Dr. Hood," he cried enthusiastically, "you are a great poet! You have called an uncreated being out of the void. How much more godlike that is than if you had only ferreted out the mere facts! Indeed, the mere facts are rather commonplace and comic by comparison."
"I have no notion what you are talking about," said Dr. Hood rather haughtily; "my facts are all inevitable, though necessarily incomplete. A place may be permitted to intuition, perhaps (or poetry if you prefer the term), but only because the corresponding details cannot as yet be ascertained. In the absence of Mr. Glass——"
"That's it, that's it," said the little priest, nodding quite eagerly, "that's the first idea to get fixed; the absence of Mr. Glass. He is so extremely absent. I suppose," he added reflectively, "that there was never anybody so absent as Mr. Glass."
"Do you mean he is absent from the town?" demanded the doctor.
"I mean he is absent from everywhere," answered Father Brown; "he is absent from the Nature of Things, so to speak."
"Do you seriously mean," said the specialist with a smile, "that there is no such person?"
The priest made a sign of assent. "It does seem a pity," he said.
Orion Hood broke into a contemptuous laugh. "Well," he said, "before we go on to the hundred and one other evidences, let us take the first proof we found; the first fact we fell over when we fell into this room. If there is no Mr. Glass, whose hat is this?"
"It is Mr. Todhunter's," replied Father Brown.
"But it doesn't fit him," cried Hood impatiently. "He couldn't possibly wear it!"
Father Brown shook his head with ineffable mildness. "I never said he could wear it," he answered. "I said it was his hat. Or, if you insist on a shade of difference, a hat that is his."
"And what is the shade of difference?" asked the criminologist with a slight sneer.
"My good sir," cried the mild little man, with his first movement akin to impatience, "if you will walk down the street to the nearest hatter's shop, you will see that there is, in common speech, a difference between a man's hat and the hats that are his."
"But a hatter," protested Hood, "can get money out of his stock of new hats. What could Todhunter get out of this one old hat?"
"Rabbits," replied Father Brown promptly.
"What?" cried Dr. Hood.
"Rabbits, ribbons, sweetmeats, goldfish, rolls of coloured paper," said the reverend gentleman with rapidity. "Didn't you see it all when you found out the faked ropes? It's just the same with the sword. Mr. Todhunter hasn't got a scratch on him, as you say; but he's got a scratch in him, if you follow me."
"Do you mean inside Mr. Todhunter's clothes?" inquired Mrs. MacNab sternly.
"I do not mean inside Mr. Todhunter's clothes," said Father Brown. "I mean inside Mr. Todhunter."
"Well, what in the name of Bedlam do you mean?"
"Mr. Todhunter," explained Father Brown placidly, "is learning to be a professional conjurer, as well as juggler, ventriloquist, and expert in the rope trick. The conjuring explains the hat. It is without traces of hair, not because it is worn by the prematurely bald Mr. Glass, but because it has never been worn by anybody. The juggling explains the three glasses, which Todhunter was teaching himself