M. MAURICE BRUN and M. Armand Armagnac were crossing the sunlit Champs Elysee with a kind of vivacious respectability. They were both short, brisk and bold. They both had black beards that did not seem to belong to their faces, after the strange French fashion which makes real hair look like artificial. M. Brun had a dark wedge of beard apparently affixed under his lower lip. M. Armagnac, by way of a change, had two beards; one sticking out from each corner of his emphatic chin. They were both young. They were both atheists, with a depressing fixity of outlook but great mobility of exposition. They were both pupils of the great Dr Hirsch, scientist, publicist and moralist.

M. Brun had become prominent by his proposal that the common expression “Adieu” should be obliterated from all the French classics, and a slight fine imposed for its use in private life. “Then,” he said, “the very name of your imagined God will have echoed for the last time in the ear of man.” M. Armagnac specialized rather in a resistance to militarism, and wished the chorus of the Marseillaise altered from “Aux armes, citoyens” to “Aux greves, citoyens”. But his antimilitarism was of a peculiar and Gallic sort. An eminent and very wealthy English Quaker, who had come to see him to arrange for the disarmament of the whole planet, was rather distressed by Armagnac’s proposal that (by way of beginning) the soldiers should shoot their officers.

And indeed it was in this regard that the two men differed most from their leader and father in philosophy. Dr Hirsch, though born in France and covered with the most triumphant favours of French education, was temperamentally of another type—mild, dreamy, humane; and, despite his sceptical system, not devoid of transcendentalism. He was, in short, more like a German than a Frenchman; and much as they admired him, something in the subconsciousness of these Gauls was irritated at his pleading for peace in so peaceful a manner. To their party throughout Europe, however, Paul Hirsch was a saint of science. His large and daring cosmic theories advertised his austere life and innocent, if somewhat frigid, morality; he held something of the position of Darwin doubled with the position of Tolstoy. But he was neither an anarchist nor an antipatriot; his views on disarmament were moderate and evolutionary—the Republican Government put considerable confidence in him as to various chemical improvements. He had lately even discovered a noiseless explosive, the secret of which the Government was carefully guarding.

His house stood in a handsome street near the Elysee—a street which in that strong summer seemed almost as full of foliage as the park itself; a row of chestnuts shattered the sunshine, interrupted only in one place where a large cafe ran out into the street. Almost opposite to this were the white and green blinds of the great scientist’s house, an iron balcony, also painted green, running along in front of the first-floor windows. Beneath this was the entrance into a kind of court, gay with shrubs and tiles, into which the two Frenchmen passed in animated talk.

The door was opened to them by the doctor’s old servant, Simon, who might very well have passed for a doctor himself, having a strict suit of black, spectacles, grey hair, and a confidential manner. In fact, he was a far more presentable man of science than his master, Dr Hirsch, who was a forked radish of a fellow, with just enough bulb of a head to make his body insignificant. With all the gravity of a great physician handling a prescription, Simon handed a letter to M. Armagnac. That gentleman ripped it up with a racial impatience, and rapidly read the following:

I cannot come down to speak to you. There is a man in this house whom I refuse to meet. He is a Chauvinist officer, Dubosc. He is sitting on the stairs. He has been kicking the furniture about in all the other rooms; I have locked myself in my study, opposite that cafe. If you love me, go over to the cafe and wait at one of the tables outside. I will try to send him over to you. I want you to answer him and deal with him. I cannot meet him myself. I cannot: I will not.

There is going to be another Dreyfus case.

P. HIRSCH

M. Armagnac looked at M. Brun. M. Brun borrowed the letter, read it, and looked at M. Armagnac. Then both betook themselves briskly to one of the little tables under the chestnuts opposite, where they procured two tall glasses of horrible green absinthe, which they could drink apparently in any weather and at any time. Otherwise the cafe seemed empty, except for one soldier drinking coffee at one table, and at another a large man drinking a small syrup and a priest drinking nothing.

Maurice Brun cleared his throat and said: “Of course we must help the master in every way, but—”

There was an abrupt silence, and Armagnac said: “He may have excellent reasons for not meeting the man himself, but—”

Before either could complete a sentence, it was evident that the invader had been expelled from the house opposite. The shrubs under the archway swayed and burst apart, as that unwelcome guest was shot out of them like a cannon-ball.

He was a sturdy figure in a small and tilted Tyrolean felt hat, a figure that had indeed something generally Tyrolean about it. The man’s shoulders were big and broad, but his legs were neat and active in knee-breeches and knitted stockings. His face was brown like a nut; he had very bright and restless brown eyes; his dark hair was brushed back stiffly in front and cropped close behind, outlining a square and powerful skull; and he had a huge black moustache like the horns of a bison. Such a substantial head is generally based on a bull neck; but this was hidden by a big coloured scarf, swathed round up the man’s ears and falling in front inside his jacket like a sort of fancy waistcoat. It was a scarf of strong dead colours, dark red and old gold and purple, probably of Oriental fabrication. Altogether the man had something a shade barbaric about him; more like a Hungarian squire than an ordinary French officer. His French, however, was obviously that of a native; and his French patriotism was so impulsive as to be slightly absurd. His first act when he burst out of the archway was to call in a clarion voice down the street: “Are there any Frenchmen here?” as if he were calling for Christians in Mecca.

Armagnac and Brun instantly stood up; but they were too late. Men were already running from the street corners; there was a small but ever-clustering crowd. With the prompt French instinct for the politics of the street, the man with the black moustache had already run across to a corner of the cafe, sprung on one of the tables, and seizing a branch of chestnut to steady himself, shouted as Camille Desmoulins once shouted when he scattered the oak-leaves among the populace.

“Frenchmen!” he volleyed; “I cannot speak! God help me, that is why I am speaking! The fellows in their filthy parliaments who learn to speak also learn to be silent—silent as that spy cowering in the house opposite! Silent as he is when I beat on his bedroom door! Silent as he is now, though he hears my voice across this street and shakes where he sits! Oh, they can be silent eloquently—the politicians! But the time has come when we that cannot speak must speak. You are betrayed to the Prussians. Betrayed at this moment. Betrayed by that man. I am Jules Dubosc, Colonel of Artillery, Belfort. We caught a German spy in the Vosges yesterday, and a paper was found on him—a paper I hold in my hand. Oh, they tried to hush it up; but I took it direct to the man who wrote it—the man in that house! It is in his hand. It is signed with his initials. It is a direction for finding the secret of this new Noiseless Powder. Hirsch invented it; Hirsch wrote this note about it. This note is in German, and was found in a German’s pocket. ‘Tell the man the formula for powder is in grey envelope in first drawer to the left of Secretary’s desk, War Office, in red ink. He must be careful. P.H.’”

He rattled short sentences like a quick-firing gun, but he was plainly the sort of man who is either mad or right. The mass of the crowd was Nationalist, and already in threatening uproar; and a minority of equally angry Intellectuals, led by Armagnac and Brun, only made the majority more militant.

“If this is a military secret,” shouted Brun, “why do you yell about it in the street?”

“I will tell you why I do!” roared Dubosc above the roaring crowd. “I went to this man in straight and civil style. If he had any explanation it could have been given in complete confidence. He refuses to explain. He refers me to two strangers in a cafe as to two flunkeys. He has thrown me out of the house, but I am going back into it, with the people of Paris behind me!”

A shout seemed to shake the very facade of mansions and two stones flew, one breaking a window above the balcony. The indignant Colonel plunged once more under the archway and was heard crying and thundering inside. Every instant the human sea grew wider and wider; it surged up against the rails and steps of the traitor’s house; it was already certain that the place would be burst into like the Bastille, when the broken french window opened and Dr Hirsch came out on the balcony. For an instant the fury half turned to laughter; for he was an absurd figure in such a scene. His long bare neck and sloping shoulders were the shape of a champagne bottle, but that was the only festive thing about him. His coat hung on him as on a peg; he wore his carrot-coloured hair long and weedy; his cheeks and chin were fully fringed with one of those irritating beards that begin far from the mouth. He was very pale, and he wore blue spectacles.

Livid as he was, he spoke with a sort of prim decision, so that the mob fell silent in the middle of his third sentence.

“...only two things to say to you now. The first is to my foes, the second to my friends. To my foes I say: It is true I will not meet M. Dubosc, though he is storming outside this very room. It is true I have asked two other men to confront him for me. And I will tell you why! Because I will not and must not see him—because it would be against all rules of dignity and honour to see him. Before I am triumphantly cleared before a court, there is another arbitration this gentleman owes me as a gentleman, and in referring him to my seconds I am strictly—”

Armagnac and Brun were waving their hats wildly, and even the Doctor’s enemies roared applause at this unexpected defiance. Once more a few sentences were inaudible, but they could hear him say: “To my friends—I myself should always prefer weapons purely intellectual, and to these an evolved humanity will certainly confine itself. But our own most precious truth is the fundamental force of matter and heredity. My books are successful; my theories are unrefuted; but I suffer in politics from a prejudice almost physical in the French. I cannot speak like Clemenceau and Deroulede, for their words are like echoes of their pistols. The French ask for a duellist as the English ask for a sportsman. Well, I give my proofs: I will pay this barbaric bribe, and then go back to reason for the rest of my life.”

Two men were instantly found in the crowd itself to offer their services to Colonel Dubosc, who came out presently, satisfied. One was the common soldier with the coffee, who said simply: “I will act for you, sir. I am the Duc de Valognes.” The other was the big man, whom his friend the priest sought at first to dissuade; and then walked away alone.

In the early evening a light dinner was spread at the back of the Cafe Charlemagne. Though unroofed by any glass or gilt plaster, the guests were nearly all under a delicate and irregular roof of leaves; for the ornamental trees stood so thick around and among the tables as to give something of the dimness and the dazzle of a small orchard. At one of the central tables a very stumpy little priest sat in complete solitude, and applied himself to a pile of whitebait with the gravest sort of enjoyment. His daily living being very plain, he had a peculiar taste for sudden and isolated luxuries; he was an abstemious epicure. He did not lift his eyes from his plate, round which red pepper, lemons, brown bread and butter, etc., were rigidly ranked, until a tall shadow fell across the table, and his friend Flambeau sat down opposite. Flambeau was gloomy.

“I’m afraid I must chuck this business,” said he heavily. “I’m all on the side of the French soldiers like Dubosc, and I’m all against the French atheists like Hirsch; but it seems to me in this case we’ve made a mistake. The Duke and I thought it as well to investigate the charge, and I must say I’m glad we did.”

“Is the paper a forgery, then?” asked the priest

“That’s just the odd thing,” replied Flambeau. “It’s exactly like Hirsch’s writing, and nobody can point out any mistake in it. But it wasn’t written by Hirsch. If he’s a French patriot he didn’t write it, because it gives information to Germany. And if he’s a German spy he didn’t write it, well—because it doesn’t give information to Germany.”

“You mean the information is wrong?” asked Father Brown.

“Wrong,” replied the other, “and wrong exactly where Dr Hirsch would have been right—about the hiding-place of his own secret formula in his own official department. By favour of Hirsch and the authorities, the Duke and I have actually been allowed to inspect the secret drawer at the War Office where the Hirsch formula is kept. We are the only people who have ever known it, except the inventor himself and the Minister for War; but the Minister permitted it to save Hirsch from fighting. After that we really can’t support Dubosc if his revelation is a mare’s nest.”

“And it is?” asked Father Brown.

“It is,” said his friend gloomily. “It is a clumsy forgery by somebody who knew nothing of the real hiding-place. It says the paper is in the cupboard on the right of the Secretary’s desk. As a fact the cupboard with the secret drawer is some way to the left of the desk. It says the grey envelope contains a long document written in red ink. It isn’t written in red ink, but in ordinary black ink. It’s manifestly absurd to say that Hirsch can have made a mistake about a paper that nobody knew of but himself; or can have tried to help a foreign thief by telling him to fumble in the wrong drawer. I think we must chuck it up and apologize to old Carrots.”

Father Brown seemed to cogitate; he lifted a little whitebait on his fork. “You are sure the grey envelope was in the left cupboard?” he asked.

“Positive,” replied Flambeau. “The grey envelope—it was a white envelope really—was—”

Father Brown put down the small silver fish and the fork and stared across at his companion. “What?” he asked, in an altered voice.

“Well, what?” repeated Flambeau, eating heartily.

“It was not grey,” said the priest. “Flambeau, you frighten me.”

“What the deuce are you frightened of?”

“I’m frightened of a white envelope,” said the other seriously, “If it had only just been grey! Hang it all, it might as well have been grey. But if it was white, the whole business is black. The Doctor has been dabbling in some of the old brimstone after all.”

“But I tell you he couldn’t have written such a note!” cried Flambeau. “The note is utterly wrong about the facts. And innocent or guilty, Dr Hirsch knew all about the facts.”

“The man who wrote that note knew all about the facts,” said his clerical companion soberly. “He could never have got ‘em so wrong without knowing about ‘em. You have to know an awful lot to be wrong on every subject—like the devil.”

“Do you mean—?”

“I mean a man telling lies on chance would have told some of the truth,” said his friend firmly. “Suppose someone sent you to find a house with a green door and a blue blind, with a front garden but no back garden, with a dog but no cat, and where they drank coffee but not tea. You would say if you found no such house that it was all made up. But I say no. I say if you found a house where the door was blue and the blind green, where there was a back garden and no front garden, where cats were common and dogs instantly shot, where tea was drunk in quarts and coffee forbidden—then you would know you had found the house. The man must have known that particular house to be so accurately inaccurate.”

“But what could it mean?” demanded the diner opposite.

“I can’t conceive,” said Brown; “I don’t understand this Hirsch affair at all. As long as it was only the left drawer instead of the right, and red ink instead of black, I thought it must be the chance blunders of a forger, as you say. But three is a mystical number; it finishes things. It finishes this. That the direction about the drawer, the colour of ink, the colour of envelope, should none of them be right by accident, that can’t be a coincidence. It wasn’t.”

“What was it, then? Treason?” asked Flambeau, resuming his dinner.

“I don’t know that either,” answered Brown, with a face of blank bewilderment. “The only thing I can think of.... Well, I never understood that Dreyfus case. I can always grasp moral evidence easier than the other sorts. I go by a man’s eyes and voice, don’t you know, and whether his family seems happy, and by what subjects he chooses—and avoids. Well, I was puzzled in the Dreyfus case. Not by the horrible things imputed both ways; I know (though it’s not modern to say so) that human nature in the highest places is still capable of being Cenci or Borgia. No—, what puzzled me was the sincerity of both parties. I don’t mean the political parties; the rank and file are always roughly honest, and often duped. I mean the persons of the play. I mean the conspirators, if they were conspirators. I mean the traitor, if he was a traitor. I mean the men who must have known the truth. Now Dreyfus went on like a man who knew he was a wronged man. And yet the French statesmen and soldiers went on as if they knew he wasn’t a wronged man but simply a wrong ‘un. I don’t mean they behaved well; I mean they behaved as if they were sure. I can’t describe these things; I know what I mean.”

“I wish I did,” said his friend. “And what has it to do with old Hirsch?”

“Suppose a person in a position of trust,” went on the priest, “began to give the enemy information because it was false information. Suppose he even thought he was saving his country by misleading the foreigner. Suppose this brought him into spy circles, and little loans were made to him, and little ties tied on to him. Suppose he kept up his contradictory position in a confused way by never telling the foreign spies the truth, but letting it more and more be guessed. The better part of him (what was left of it) would still say: ‘I have not helped the enemy; I said it was the left drawer.’ The meaner part of him would already be saying: ‘But they may have the sense to see that means the right.’ I think it is psychologically possible—in an enlightened age, you know.”

“It may be psychologically possible,” answered Flambeau, “and it certainly would explain Dreyfus being certain he was wronged and his judges being sure he was guilty. But it won’t wash historically, because Dreyfus’s document (if it was his document) was literally correct.”

“I wasn’t thinking of Dreyfus,” said Father Brown.

Silence had sunk around them with the emptying of the tables; it was already late, though the sunlight still clung to everything, as if accidentally entangled in the trees. In the stillness Flambeau shifted his seat sharply—making an isolated and echoing noise—and threw his elbow over the angle of it. “Well,” he said, rather harshly, “if Hirsch is not better than a timid treason-monger...”

“You mustn’t be too hard on them,” said Father Brown gently. “It’s not entirely their fault; but they have no instincts. I mean those things that make a woman refuse to dance with a man or a man to touch an investment. They’ve been taught that it’s all a matter of degree.”

“Anyhow,” cried Flambeau impatiently, “he’s not a patch on my principal; and I shall go through with it. Old Dubosc may be a bit mad, but he’s a sort of patriot after all.”

Father Brown continued to consume whitebait.

Something in the stolid way he did so caused Flambeau’s fierce black eyes to ramble over his companion afresh. “What’s the matter with you?” Flambeau demanded. “Dubosc’s all right in that way. You don’t doubt him?”

“My friend,” said the small priest, laying down his knife and fork in a kind of cold despair, “I doubt everything. Everything, I mean, that has happened today. I doubt the whole story, though it has been acted before my face. I doubt every sight that my eyes have seen since morning. There is something in this business quite different from the ordinary police mystery where one man is more or less lying and the other man more or less telling the truth. Here both men.... Well! I’ve told you the only theory I can think of that could satisfy anybody. It doesn’t satisfy me.”

“Nor me either,” replied Flambeau frowning, while the other went on eating fish with an air of entire resignation. “If all you can suggest is that notion of a message conveyed by contraries, I call it uncommonly clever, but...well, what would you call it?”

“I should call it thin,” said the priest promptly. “I should call it uncommonly thin. But that’s the queer thing about the whole business. The lie is like a schoolboy’s. There are only three versions, Dubosc’s and Hirsch’s and that fancy of mine. Either that note was written by a French officer to ruin a French official; or it was written by the French official to help German officers; or it was written by the French official to mislead German officers. Very well. You’d expect a secret paper passing between such people, officials or officers, to look quite different from that. You’d expect, probably a cipher, certainly abbreviations; most certainly scientific and strictly professional terms. But this thing’s elaborately simple, like a penny dreadful: ‘In the purple grotto you will find the golden casket.’ It looks as if... as if it were meant to be seen through at once.”

Almost before they could take it in a short figure in French uniform had walked up to their table like the wind, and sat down with a sort of thump.

“I have extraordinary news,” said the Duc de Valognes. “I have just come from this Colonel of ours. He is packing up to leave the country, and he asks us to make his excuses sur le terrain.”

“What?” cried Flambeau, with an incredulity quite frightful—“apologize?”

“Yes,” said the Duke gruffly; “then and there—before everybody—when the swords are drawn. And you and I have to do it while he is leaving the country.”

“But what can this mean?” cried Flambeau. “He can’t be afraid of that little Hirsch! Confound it!” he cried, in a kind of rational rage; “nobody could be afraid of Hirsch!”

“I believe it’s some plot!” snapped Valognes—“some plot of the Jews and Freemasons. It’s meant to work up glory for Hirsch...”

The face of Father Brown was commonplace, but curiously contented; it could shine with ignorance as well as with knowledge. But there was always one flash when the foolish mask fell, and the wise mask fitted itself in its place; and Flambeau, who knew his friend, knew that his friend had suddenly understood. Brown said nothing, but finished his plate of fish.

“Where did you last see our precious Colonel?” asked Flambeau, irritably.

“He’s round at the Hotel Saint Louis by the Elysee, where we drove with him. He’s packing up, I tell you.”

“Will he be there still, do you think?” asked Flambeau, frowning at the table.

“I don’t think he can get away yet,” replied the Duke; “he’s packing to go a long journey...”

“No,” said Father Brown, quite simply, but suddenly standing up, “for a very short journey. For one of the shortest, in fact. But we may still be in time to catch him if we go there in a motor-cab.”

Nothing more could be got out of him until the cab swept round the corner by the Hotel Saint Louis, where they got out, and he led the party up a side lane already in deep shadow with the growing dusk. Once, when the Duke impatiently asked whether Hirsch was guilty of treason or not, he answered rather absently: “No; only of ambition—like Caesar.” Then he somewhat inconsequently added: “He lives a very lonely life; he has had to do everything for himself.”

“Well, if he’s ambitious, he ought to be satisfied now,” said Flambeau rather bitterly. “All Paris will cheer him now our cursed Colonel has turned tail.”

“Don’t talk so loud,” said Father Brown, lowering his voice, “your cursed Colonel is just in front.”

The other two started and shrank farther back into the shadow of the wall, for the sturdy figure of their runaway principal could indeed be seen shuffling along in the twilight in front, a bag in each hand. He looked much the same as when they first saw him, except that he had changed his picturesque mountaineering knickers for a conventional pair of trousers. It was clear he was already escaping from the hotel.

The lane down which they followed him was one of those that seem to be at the back of things, and look like the wrong side of the stage scenery. A colourless, continuous wall ran down one flank of it, interrupted at intervals by dull-hued and dirt-stained doors, all shut fast and featureless save for the chalk scribbles of some passing gamin. The tops of trees, mostly rather depressing evergreens, showed at intervals over the top of the wall, and beyond them in the grey and purple gloaming could be seen the back of some long terrace of tall Parisian houses, really comparatively close, but somehow looking as inaccessible as a range of marble mountains. On the other side of the lane ran the high gilt railings of a gloomy park.

Flambeau was looking round him in rather a weird way. “Do you know,” he said, “there is something about this place that—”

“Hullo!” called out the Duke sharply; “that fellow’s disappeared. Vanished, like a blasted fairy!”

“He has a key,” explained their clerical friend. “He’s only gone into one of these garden doors,” and as he spoke they heard one of the dull wooden doors close again with a click in front of them.

Flambeau strode up to the door thus shut almost in his face, and stood in front of it for a moment, biting his black moustache in a fury of curiosity. Then he threw up his long arms and swung himself aloft like a monkey and stood on the top of the wall, his enormous figure dark against the purple sky, like the dark tree-tops.

The Duke looked at the priest. “Dubosc’s escape is more elaborate than we thought,” he said; “but I suppose he is escaping from France.”

“He is escaping from everywhere,” answered Father Brown.

Valognes’s eyes brightened, but his voice sank. “Do you mean suicide?” he asked.

“You will not find his body,” replied the other.

A kind of cry came from Flambeau on the wall above. “My God,” he exclaimed in French, “I know what this place is now! Why, it’s the back of the street where old Hirsch lives. I thought I could recognize the back of a house as well as the back of a man.”

“And Dubosc’s gone in there!” cried the Duke, smiting his hip. “Why, they’ll meet after all!” And with sudden Gallic vivacity he hopped up on the wall beside Flambeau and sat there positively kicking his legs with excitement. The priest alone remained below, leaning against the wall, with his back to the whole theatre of events, and looking wistfully across to the park palings and the twinkling, twilit trees.

The Duke, however stimulated, had the instincts of an aristocrat, and desired rather to stare at the house than to spy on it; but Flambeau, who had the instincts of a burglar (and a detective), had already swung himself from the wall into the fork of a straggling tree from which he could crawl quite close to the only illuminated window in the back of the high dark house. A red blind had been pulled down over the light, but pulled crookedly, so that it gaped on one side, and by risking his neck along a branch that looked as treacherous as a twig, Flambeau could just see Colonel Dubosc walking about in a brilliantly-lighted and luxurious bedroom. But close as Flambeau was to the house, he heard the words of his colleagues by the wall, and repeated them in a low voice.

“Yes, they will meet now after all!”

“They will never meet,” said Father Brown. “Hirsch was right when he said that in such an affair the principals must not meet. Have you read a queer psychological story by Henry James, of two persons who so perpetually missed meeting each other by accident that they began to feel quite frightened of each other, and to think it was fate? This is something of the kind, but more curious.”

“There are people in Paris who will cure them of such morbid fancies,” said Valognes vindictively. “They will jolly well have to meet if we capture them and force them to fight.”

“They will not meet on the Day of Judgement,” said the priest. “If God Almighty held the truncheon of the lists, if St Michael blew the trumpet for the swords to cross—even then, if one of them stood ready, the other would not come.”

“Oh, what does all this mysticism mean?” cried the Duc de Valognes, impatiently; “why on earth shouldn’t they meet like other people?”

“They are the opposite of each other,” said Father Brown, with a queer kind of smile. “They contradict each other. They cancel out, so to speak.”

He continued to gaze at the darkening trees opposite, but Valognes turned his head sharply at a suppressed exclamation from Flambeau. That investigator, peering into the lighted room, had just seen the Colonel, after a pace or two, proceed to take his coat off. Flambeau’s first thought was that this really looked like a fight; but he soon dropped the thought for another. The solidity and squareness of Dubosc’s chest and shoulders was all a powerful piece of padding and came off with his coat. In his shirt and trousers he was a comparatively slim gentleman, who walked across the bedroom to the bathroom with no more pugnacious purpose than that of washing himself. He bent over a basin, dried his dripping hands and face on a towel, and turned again so that the strong light fell on his face. His brown complexion had gone, his big black moustache had gone; he—was clean-shaven and very pate. Nothing remained of the Colonel but his bright, hawk-like, brown eyes. Under the wall Father Brown was going on in heavy meditation, as if to himself.

“It is all just like what I was saying to Flambeau. These opposites won’t do. They don’t work. They don’t fight. If it’s white instead of black, and solid instead of liquid, and so on all along the line—then there’s something wrong, Monsieur, there’s something wrong. One of these men is fair and the other dark, one stout and the other slim, one strong and the other weak. One has a moustache and no beard, so you can’t see his mouth; the other has a beard and no moustache, so you can’t see his chin. One has hair cropped to his skull, but a scarf to hide his neck; the other has low shirt-collars, but long hair to bide his skull. It’s all too neat and correct, Monsieur, and there’s something wrong. Things made so opposite are things that cannot quarrel. Wherever the one sticks out the other sinks in. Like a face and a mask, like a lock and a key...”

Flambeau was peering into the house with a visage as white as a sheet. The occupant of the room was standing with his back to him, but in front of a looking-glass, and had already fitted round his face a sort of framework of rank red hair, hanging disordered from the head and clinging round the jaws and chin while leaving the mocking mouth uncovered. Seen thus in the glass the white face looked like the face of Judas laughing horribly and surrounded by capering flames of hell. For a spasm Flambeau saw the fierce, red-brown eyes dancing, then they were covered with a pair of blue spectacles. Slipping on a loose black coat, the figure vanished towards the front of the house. A few moments later a roar of popular applause from the street beyond announced that Dr Hirsch had once more appeared upon the balcony.