Whether or not this case has an historical interest is a matter of conjecture. If it has none, then the title I have given it is a misnomer. But I think the conjecture that some historical interest attaches to it is by no means an empty one, and all that can be urged against it is the common though not always declared error that romance expired fifty years at least ago, and history with it. This makes it seem improbable that the answer to an unsolved riddle of a century since should be found to-day in an inquiry agent\'s dingy office in Bedford Street, Covent Garden. Whether or not it has so been found the reader may judge for himself, though the evidence stops far short of actual proof of the identity of the "Mirror of Portugal" with the stone wherewith this case was concerned.

But first, as to the "Mirror of Portugal." This was a diamond of much and ancient fame. It was of Indian origin, and it had lain in the possession of the royal family of Portugal in the time of Portugal\'s ancient splendour. But three hundred years ago, after the extinction of the early line of succession, the diamond, with other jewels, fell into the possession of Don Antonio, one of the half-dozen pretenders who were then scrambling for the throne. Don Antonio, badly in want of money, deposited the stone in pledge with Queen Elizabeth of England, and never redeemed it. Thus it took its place as one of the English Crown jewels, and so remained till the overthrow and death of Charles the First. Queen Henrietta then carried it with her to France, and there, to obtain money to satisfy her creditors, she sold it to the great Cardinal Mazarin. He bequeathed it, at his death, to the French Crown, and among the Crown jewels of France it once more found a temporary abiding place. But once more it brought disaster with it in the shape of a revolution, and again a king lost his head at the executioner\'s hands. And in the riot and confusion of the great Revolution of 1792 the "Mirror of Portugal," with other jewels, vanished utterly. Where it went to, and who took it, nobody ever knew. The "Mirror of Portugal" disappeared as suddenly and effectually as though fused to vapour by electric combustion.

So much for the famous "Mirror." Whether or not its history is germane to the narrative which follows, probably nobody will ever certainly know. But that Dorrington considered that it was, his notes on the case abundantly testify.

For some days before Dorrington\'s attention was in any way given to this matter, a poorly-dressed and not altogether prepossessing Frenchman had been haunting the staircase and tapping at the office door, unsuccessfully attempting an interview with Dorrington, who happened to be out, or busy, whenever he called. The man never asked for Hicks, Dorrington\'s partner; but this was very natural. In the first place, it was always Dorrington who met all strangers and conducted all negotiations, and in the second, Dorrington had just lately, in a case regarding a secret society in Soho, made his name much known and respected, not to say feared, in the foreign colony of that quarter; wherefore it was likely that a man who bore evidence of residence in that neighbourhood should come with the name of Dorrington on his tongue.

The weather was cold, but the man\'s clothes were thin and threadbare, and he had no overcoat. His face was of a broad, low type, coarse in feature and small in forehead, and he wore the baggy black linen peaked cap familiar on the heads of men of his class in parts of Paris. He had called unsuccessfully, as I have said, sometimes once, sometimes more frequently, on each of three or four days before he succeeded in seeing Dorrington. At last, however, he intercepted him on the stairs, as Dorrington arrived at about eleven in the morning.

"Pardon, m\'sieu," he said, laying his finger on Dorrington\'s arm, "it is M. Dorrington—not?"

"Well—suppose it is, what then?" Dorrington never admitted his identity to a stranger without first seeing good cause.

"I \'ave beesness—very great beesness; beesness of a large profit for you if you please to take it. Where shall I tell it?"

"Come in here," Dorrington replied, leading the way to his private room. The man did not look like a wealthy client, but that signified nothing. Dorrington had made profitable strokes after introductions even less promising.

The man followed Dorrington, pulled off his cap, and sat in the chair Dorrington pointed at.

"In the first place," said Dorrington, "what\'s your name?"

"Ah, yas—but before—all that I tell is for ourselves alone, is it not? It is all in confidence, eh?"

"Yes, yes, of course," Dorrington answered, with virtuous impatience. "Whatever is said in this room is regarded as strictly confidential. What\'s your name?"

"Jacques Bouvier."

"Living at——?"

"Little Norham Street, Soho."

"And now the business you speak of."

"The beesness is this. My cousin, Léon Bouvier—he is coquin—a rrrascal!"

"Very likely."

"He has a great jewel—it is, I have no doubt, a diamond—of a great value. It is not his! There is no right of him to it! It should be mine. If you get it for me one-quarter of it in money shall be yours! And it is of a great value."

"Where does your cousin live? What is he?"

"Beck Street, Soho. He has a shop—a café—Café des Bons Camarades. And he give me not a crrrust—if I starve!"

It scarcely seemed likely that the keeper of a little foreign café in a back street of Soho would be possessed of a jewel a quarter of whose value would be prize enough to tempt Dorrington to take a new case up. But Dorrington bore with the man a little longer. "What is this jewel you talk of?" he asked. "And if you don\'t know enough about it to be quite sure whether it is a diamond or not, what do you know?"

"Listen! The stone I have never seen; but that it is a diamond makes probable. What else so much value? And it is much value that gives my cousin so great care and trouble—cochon! Listen! I relate to you. My father—he was charcoal-burner at Bonneuil, department of Seine. My uncle—the father of my cousin—also was charcoal-burner. The grandfather—charcoal-burner also; and his father and his grandfather before him—all burners of charcoal, at Bonneuil. Now perceive. The father of my grandfather was of the great Revolution—a young man, great among those who stormed the Bastille, the Tuileries, the H?tel de Ville, brave, and a leader. Now, when palaces were burnt and heads were falling there was naturally much confusion. Things were lost—things of large value. What more natural? While so many were losing the head from the shoulders, it was not strange that some should lose jewels from the neck. And when these things were lost, who might have a greater right to keep them than the young men of the Revolution, the brave, and the leaders, they who did the work?"

"If you mean that your respectable great-grandfather stole something, you needn\'t explain it any more," Dorrington said. "I quite understand."

"I do not say stole; when there is a great revolution a thing is anybody\'s. But it would not be convenient to tell of it at the time, for the new Government might believe everything to be its own. These things I do not know, you will understand—I suggest an explanation, that is all. After the great Revolution, my great-grandfather lives alone and quiet, and burns the charcoal as before. Why? The jewel is too great to sell so soon. So he gives it to his son and dies. He also, my grandfather, still burns the charcoal. Again, why? Because, as I believe, he is too poor, too common a man to go about openly to sell so great a stone. More, he loves the stone, for with that he is always rich; and so he burns his charcoal and lives contented as his father had done, and he is rich, and nobody knows it. What then? He has two sons. When he dies, which son does he leave the stone to? Each one says it is for himself—that is natural. I say it was for my father. But however that may make itself, my father dies suddenly. He falls in a pit—by accident, says his brother; not by accident, says my mother; and soon after, she dies too. By accident too, perhaps you ask? Oh yes, by accident too, no doubt." The man laughed disagreeably. "So I am left alone, a little boy, to burn charcoal. When I am a bigger boy there comes the great war, and the Prussians besiege Paris. My uncle, he, burning charcoal no more, goes at night, and takes things from the dead Prussians. Perhaps they are not always quite dead when he finds them—perhaps he makes them so. Be that as it will, the Prussians take him one dark night; and they stand him against a garden wall, and pif! paf! they shoot him. That is all of my uncle; but he dies a rich man, and nobody knows. What does his wife do? She has the jewel, and she has a little money that has been got from the dead Prussians. So when the war is over, she comes to London with my cousin, the bad Léon, and she has the café—Café des Bons Camarades. And Léon grows up, and his mother dies, and he has the café, and with the jewel is a rich man—nobody knowing; nobody but me. But, figure to yourself; shall I burn charcoal and starve at Bonneuil with a rich cousin in London—rich with a diamond that should be mine? Not so. I come over, and Léon, at first he lets me wait at the café. But I do not want that—there is the stone, and I can never see it, never find it. So one day Léon finds me looking in a box, and—chut! out I go. I tell Léon that I will share the jewel with him or I will tell the police. He laughs at me—there is no jewel, he says—I am mad. I do not tell the police, for that is to lose it altogether. But I come here and I offer you one quarter of the diamond if you shall get it."

"Steal it for you, eh?"

Jacques Bouvier shrugged his shoulders. "The word is as you please," he said. "The jewel is not his. And if there is delay it will be gone. Already he goes each day to Hatton Garden, leaving his wife to keep the Café des Bons Camarades. Perhaps he is selling the jewel to-day! Who can tell? So that it will be well that you begin at once."

"Very well. My fee in advance will be twenty guineas."

"What? Dieu!—I have no money, I tell you! Get the diamond, and there is one quarter—twenty-five per cent.—for you!"

"But what guarantee do you give that this story of yours isn\'t all a hoax? Can you expect me to take everything on trust, and work for nothing?"

The man rose and waved his arms excitedly. "It is true, I say!" he exclaimed. "It is a fortune! There is much for you, and it will pay! I have no money, or you should have some. What can I do? You will lose the chance if you are foolish!"

"It rather seems to me, my friend, that I shall be foolish to give valuable time to gratifying your cock-and-bull fancies. See here now. I\'m a man of business, and my time is fully occupied. You come here and waste half an hour or more of it with a long rigmarole about some valuable article that you say yourself you have never seen, and you don\'t even know whether it is a diamond or not. You wander at large over family traditions which you may believe yourself or may not. You have no money, and you offer no fee as a guarantee of your bona fides, and the sum of the thing is that you ask me to go and commit a theft—to purloin an article you can\'t even describe, and then to give you three-quarters of the proceeds. No, my man, you have made a mistake. You must go away from here at once, and if I find you hanging about my door again I shall have you taken away very summarily. Do you understand? Now go away."

"Mon Dieu! But——"

"I\'ve no more time to waste," Dorrington answered, opening the door and pointing to the stairs. "If you stay here any longer you\'ll get into trouble."

BIG FOOL

"SIR YOU ARE A VER\' BIG FOOL—A FOOL!"

Jacques Bouvier walked out, muttering and agitating his hands. At the top stair he turned and, almost too angry for words, burst out, "Sir—you are a ver\' big fool—a fool!" But Dorrington slammed the door.

He determined, however, if he could find a little time, to learn a little more of Léon Bouvier—perhaps to put a man to watch at the Café des Bons Camarades. That the keeper of this place in Soho should go regularly to Hatton Garden, the diamond market, was curious, and Dorrington had met and analysed too many extraordinary romances to put aside unexamined Jacques Bouvier\'s seemingly improbable story. But, having heard all the man had to say, it had clearly been his policy to get rid of him in the way he had done. Dorrington was quite ready to steal a diamond, or anything else of value, if it could be done quite safely, but he was no such fool as to give three-quarters of his plunder—or any of it—to somebody else. So that the politic plan was to send Jacques Bouvier away with the impression that his story was altogether pooh-poohed and was to be forgotten.

II

Dorrington left his office late that day, and the evening being clear, though dark, he walked toward Conduit Street by way of Soho; he thought to take a glance at the Café des Bons Camarades on his way, without being observed, should Jacques Bouvier be in the vicinity.

Beck Street, Soho, was a short and narrow street lying east and west, and joining two of the larger streets that stretch north and south across the district. It was even a trifle dirtier than these by-streets in that quarter are wont to be. The Café des Bons Camarades was a little green-painted shop the window whereof was backed by muslin curtains, while upon the window itself appeared in florid painted letters the words "Cuisine Fran?aise." It was the only shop in the street, with the exception of a small coal and firewood shed at one end, the other buildings consisting of the side wall of a factory, now closed for the night, and a few tenement houses. An alley entrance—apparently the gate of a stable-yard—stood next the café. As Dorrington walked by the steamy window, he was startled to hear his own name and some part of his office address spoken in excited tones somewhere in this dark alley entrance; and suddenly a man rather well dressed, and cramming a damaged tall hat on his head as he went, darted from the entrance and ran in the direction from which Dorrington had come. A stoutly built Frenchwoman, carrying on her face every indication of extreme excitement, watched him from the gateway, and Dorrington made no doubt that it was in her voice that he had heard his name mentioned. He walked briskly to the end of the short street, turned at the end, and hurried round the block of houses, in hope to catch another sight of the man. Presently he saw him, running, in Old Compton Street, and making in the direction of Charing Cross Road. Dorrington mended his pace, and followed. The man emerged where Shaftesbury Avenue meets Charing Cross Road, and, as he crossed, hesitated once or twice, as though he thought of hailing a cab, but decided rather to trust his own legs. He hastened through the byways to St. Martin\'s Lane, and Dorrington now perceived that one side and half the back of his coat was dripping with wet mud. Also it was plain, as Dorrington had suspected, that his destination was Dorrington\'s own office in Bedford Street. So the follower broke into a trot, and at last came upon the muddy man wrenching at the bell and pounding at the closed door of the house in Bedford Street, just as the housekeeper began to turn the lock.

"M\'sieu Dorrington—M\'sieu Dorrington!" the man exclaimed, excitedly, as the door was opened.

"\'E\'s gawn \'ome long ago," the caretaker growled; "you might \'a known that. Oh, \'ere \'e is though—good evenin\', sir."

"I am Mr. Dorrington," the inquiry agent said politely. "Can I do anything for you?"

"Ah yes—it is important—at once! I am robbed!"

"Just step upstairs, then, and tell me about it."

Dorrington had but begun to light the gas in his office when his visitor broke out, "I am robbed, M\'sieu Dorrington, robbed by my cousin—coquin! Rrrobbed of everything! Rrrobbed I tell you!" He seemed astonished to find the other so little excited by the intelligence.

"Let me take your coat," Dorrington said, calmly. "You\'ve had a downer in the mud, I see. Why, what\'s this?" he smelt the collar as he went toward a hat-peg. "Chloroform!"

"Ah yes—it is that rrrascal Jacques! I will tell you. This evening I go into the gateway next my house—Café des Bons Camarades—to enter by the side-door, and—paf!—a shawl is fling across my face from behind—it is pull tight—there is a knee in my back—I can catch nothing with my hand—it smell all hot in my throat—I choke and I fall over—there is no more. I wake up and I see my wife, and she take me into the house. I am all muddy and tired, but I feel—and I have lost my property—it is a diamond—and my cousin Jacques, he has done it!"

"Are you sure of that?"

"Sure? Oh yes—it is certain, I tell you—certain!"

"Then why not inform the police?"

The visitor was clearly taken aback by this question. He faltered, and looked searchingly in Dorrington\'s face. "That is not always the convenient way," he said. "I would rather that you do it. It is the diamond that I want—not to punish my cousin—thief that he is!"

Dorrington mended a quill with ostentatious care, saying encouragingly as he did so, "I can quite understand that you may not wish to prosecute your cousin—only to recover the diamond you speak of. Also I can quite understand that there may be reasons—family reasons perhaps, perhaps others—which may render it inadvisable to make even the existence of the jewel known more than absolutely necessary. For instance, there may be other claimants, Monsieur Léon Bouvier."

The visitor started. "You know my name then?" he asked. "How is that?"

Dorrington smiled the smile of a sphinx. "M. Bouvier," he said, "it is my trade to know everything—everything." He put the pen down and gazed whimsically at the other. "My agents are everywhere. You talk of the secret agent of the Russian police—they are nothing. It is my trade to know all things. For instance"—Dorrington unlocked a drawer and produced a book (it was but an office diary), and, turning its pages, went on. "Let me see—B. It is my trade, for instance, to know about the Café des Bons Camarades, established by the late Madame Bouvier, now unhappily deceased. It is my trade to know of Madame Bouvier at Bonneuil, where the charcoal was burnt, and where Madame Bouvier was unfortunately left a widow at the time of the siege of Paris, because of some lamentable misunderstanding of her husband\'s with a file of Prussian soldiers by an orchard wall. It is my trade, moreover, to know something of the sad death of that husband\'s brother—in a pit—and of the later death of his widow. Oh yes. More" (turning a page attentively, as though following detailed notes), "it is my trade to know of a little quarrel between those brothers—it might even have been about a diamond, just such a diamond as you have come about to-night—and of jewels missed from the Tuileries in the great Revolution a hundred years ago." He shut the book with a bang and returned it to its place. "And there are other things—too many to talk about," he said, crossing his legs and smiling calmly at the Frenchman.

During this long pretence at reading, Bouvier had slid farther and farther forward on his chair, till he sat on the edge, his eyes staring wide, and his chin dropped. He had been pale when he arrived, but now he was of a leaden gray. He said not a word.

Dorrington laughed lightly. "Come," he said, "I see you are astonished. Very likely. Very few of the people and families whose dossiers we have here" (he waved his hand generally about the room) "are aware of what we know. But we don\'t make a song of it, I assure you, unless it is for the benefit of clients. A client\'s affairs are sacred, of course, and our resources are at his disposal. Do I understand that you become a client?"

Bouvier sat a little farther back on his chair and closed his mouth. "A—a—yes," he answered at length, with an effort, moistening his lips as he spoke. "That is why I come."

"Ah, now we shall understand each other," Dorrington replied genially, opening an ink-pot and clearing his blotting-pad. "We\'re not connected with the police here, or anything of that sort, and except so far as we can help them we leave our client\'s affairs alone. You wish to be a client, and you wish me to recover your lost diamond. Very well, that is business. The first thing is the usual fee in advance—twenty guineas. Will you write a cheque?"

Bouvier had recovered some of his self-possession, and he hesitated. "It is a large fee," he said.

"Large? Nonsense! It is the sort of fee that might easily be swallowed up in half a day\'s expenses. And besides—a rich diamond merchant like yourself!"

Bouvier looked up quickly. "Diamond merchant?" he said. "I do not understand. I have lost my diamond—there was but one."

"And yet you go to Hatton Garden every day."

"What!" cried Bouvier, letting his hand fall from the table, "you know that too?"

"Of course," Dorrington laughed, easily; "it is my trade, I tell you. But write the cheque."

Bouvier produced a crumpled and dirty cheque-book and complied, with many pauses, looking up dazedly from time to time into Dorrington\'s face.

"Now," said Dorrington, "tell me where you kept your diamond, and all about it."

"It was in an old little wooden box—so." Bouvier, not yet quite master of himself, sketched an oblong of something less than three inches long by two broad. "The box was old and black—my grandfather may have made it, or his father. The lid fitted very tight, and the inside was packed with fine charcoal powder with the diamond resting in it. The diamond—oh, it was great; like that—so." He made another sketch, roughly square, an inch and a quarter across. "But it looked even much greater still, so bright, so wonderful! It is easy to understand that my grandfather did not sell it—beside the danger. It is so beautiful a thing, and it is such great riches—all in one little box. Why should not a poor charcoal-burner be rich in secret, and look at his diamond, and get all the few things he wants by burning his charcoal? And there was the danger. But that is long ago. I am a man of beesness, and I desired to sell it and be rich. And that Jacques—he has stolen it!"

"Let us keep to the point. The diamond was in a box. Well, where was the box?"

"On the outside of the box there were notches—so, and so. Round the box at each place there was a tight, strong, silk cord—that is two cords. The cords were round my neck, under my shirt, so. And the box was under my arm—just as a boy carries his satchel, but high up—in the armpit, where I could feel it at all times. To-night, when I come to myself, my collar was broken at the stud—see—the cords were cut—and all was gone!"

"You say your cousin Jacques has done this. How do you know?"

"Ah! But who else? Who else could know? And he has always tried to steal it. At first, I let him wait at the Café des Bons Camarades. What does he do? He prys about my house, and opens drawers; and I catch him at last looking in a box, and I turn him out. And he calls me a thief! Sacré! He goes—I have no more of him; and so—he does this!"

"Very well. Write down his name and address on this piece of paper, and your own." Bouvier did so. "And now tell me what you have been doing at Hatton Garden."

"Well, it was a very great diamond—I could not go to the first man and show it to sell. I must make myself known."

"It never struck you to get the stone cut in two, did it?"

"Eh? What?—Nom de chien! No!" He struck his knee with his hand. "Fool! Why did I not think of that? But still"—he grew more thoughtful—"I should have to show it to get it cut, and I did not know where to go. And the value would have been less."

"Just so—but it\'s the regular thing to do, I may tell you, in cases like this. But go on. About Hatton Garden, you know."

"I thought that I must make myself known among the merchants of diamonds, and then, perhaps, I should learn the ways, and one day be able to sell. As it was, I knew nothing—nothing at all. I waited, and I saved money in the café. Then, when I could do it, I dressed well and went and bought some diamonds of a dealer—very little diamonds, a little trayful for twenty pounds, and I try to sell them again. But I have paid too much—I can only sell for fifteen pounds. Then I buy more, and sell them for what I give. Then I take an office in Hatton Garden—that is, I share a room with a dealer, and there is a partition between our desks. My wife attends the café, I go to Hatton Garden to buy and sell. It loses me money, but I must lose till I can sell the great diamond. I get to know the dealers more and more, and then to-night, as I go home——" he finished with an expressive shrug and a wave of the hand.

"Yes, yes, I think I see," Dorrington said. "As to the diamond again. It doesn\'t happen to be a blue diamond, does it?"

"No—pure white; perfect."

Dorrington had asked because two especially famous diamonds disappeared from among the French Crown jewels at the time of the great Revolution. One blue, the greatest coloured diamond ever known, and the other the "Mirror of Portugal." Bouvier\'s reply made it plain that it was certainly not the first which he had just lost.

"Come," Dorrington said, "I will call and inspect the scene of your disaster. I haven\'t dined yet, and it must be well past nine o\'clock now."

They returned to Beck Street. There were gates at the dark entry by the side of the Café des Bons Camarades, but they were never shut, Bouvier explained. Dorrington had them shut now, however, and a lantern was produced. The paving was of rough cobble stones, deep in mud.

"Do many people come down here in the course of an evening?" Dorrington asked.

"Never anybody but myself."

"Very well. Stand away at your side door."

LANTERN

"DORRINGTON, WITH THE LANTERN, EXPLORED THE MUDDY COBBLE STONES."

Bouvier and his wife stood huddled and staring on the threshold of the side door, while Dorrington, with the lantern, explored the muddy cobble stones. The pieces of a broken ............