m. formery gasped: "the real track?" he muttered.

"let me show you," said guerchard. and he led him to the fireplace, and showed him the opening between the two houses.

"i must go into this myself!" cried m. formery in wild excitement.

without more ado he began to mount the steps. guerchard followed him. the duke saw their heels disappear up the steps. then he came out of the drawing-room and inquired for m. gournay-martin. he was told that the millionaire was up in his bedroom; and he went upstairs, and knocked at the door of it.

m. gournay-martin bade him enter in a very faint voice, and the duke found him lying on the bed. he was looking depressed, even exhausted, the shadow of the blusterous gournay-martin of the day before. the rich rosiness of his cheeks had faded to a moderate rose-pink.

"that telegram," moaned the millionaire. "it was the last straw. it has overwhelmed me. the coronet is lost."

"what, already?" said the duke, in a tone of the liveliest surprise.

"no, no; it's still in the safe," said the millionaire. "but it's as good as lost—before midnight it will be lost. that fiend will get it."

"if it's in this safe now, it won't be lost before midnight," said the duke. "but are you sure it's there now?"

"look for yourself," said the millionaire, taking the key of the safe from his waistcoat pocket, and handing it to the duke.

the duke opened the safe. the morocco case which held the coronet lay on the middle shell in front of him. he glanced at the millionaire, and saw that he had closed his eyes in the exhaustion of despair. whistling softly, the duke opened the case, took out the diadem, and examined it carefully, admiring its admirable workmanship. he put it back in the case, turned to the millionaire, and said thoughtfully:

"i can never make up my mind, in the case of one of these old diadems, whether one ought not to take out the stones and have them re-cut. look at this emerald now. it's a very fine stone, but this old-fashioned cutting does not really do it justice."

"oh, no, no: you should never interfere with an antique, historic piece of jewellery. any alteration decreases its value—its value as an historic relic," cried the millionaire, in a shocked tone.

"i know that," said the duke, "but the question for me is, whether one ought not to sacrifice some of its value to increasing its beauty."

"you do have such mad ideas," said the millionaire, in a tone of peevish exasperation.

"ah, well, it's a nice question," said the duke.

he snapped the case briskly, put it back on the shelf, locked the safe, and handed the key to the millionaire. then he strolled across the room and looked down into the street, whistling softly.

"i think—i think—i'll go home and get out of these motoring clothes. and i should like to have on a pair of boots that were a trifle less muddy," he said slowly.

m. gournay-martin sat up with a jerk and cried, "for heaven's sake, don't you go and desert me, my dear chap! you don't know what my nerves are like!"

"oh, you've got that sleuth-hound, guerchard, and the splendid formery, and four other detectives, and half a dozen ordinary policemen guarding you. you can do without my feeble arm. besides, i shan't be gone more than half an hour—three-quarters at the outside. i'll bring back my evening clothes with me, and dress for dinner here. i don't suppose that anything fresh will happen between now and midnight; but i want to be on the spot, and hear the information as it comes in fresh. besides, there's guerchard. i positively cling to guerchard. it's an education, though perhaps not a liberal education, to go about with him," said the duke; and there was a sub-acid irony in his voice.

"well, if you must, you must," said m. gournay-martin grumpily.

"good-bye for the present, then," said the duke. and he went out of the room and down the stairs. he took his motor-cap from the hall-table, and had his hand on the latch of the door, when the policeman in charge of it said, "i beg your pardon, sir, but have you m. guerchard's permission to leave the house?"

"m. guerchard's permission?" said the duke haughtily. "what has m. guerchard to do with me? i am the duke of charmerace." and he opened the door.

"it was m. formery's orders, your grace," stammered the policeman doubtfully.

"m. formery's orders?" said the duke, standing on the top step. "call me a taxi-cab, please."

the concierge, who stood beside the policeman, ran down the steps and blew his whistle. the policeman gazed uneasily at the duke, shifting his weight from one foot to the other; but he said no more.

a taxi-cab came up to the door, the duke went down the steps, stepped into it, and drove away.

three-quarters of an hour later he came back, having changed into clothes more suited to a paris drawing-room. he went up to the drawing-room, and there he found guerchard, m. formery, and the inspector, who had just completed their tour of inspection of the house next door and had satisfied themselves that the stolen treasures were not in it. the inspector and his men had searched it thoroughly just to make sure; but, as guerchard had foretold, the burglars had not taken the chance of the failure of the police to discover the opening between the two houses. m. formery told the duke about their tour of inspection at length. guerchard went to the telephone and told the exchange to put him through to charmerace. he was informed that the trunk line was very busy and that he might have to wait half an hour.

the duke inquired if any trace of the burglars, after they had left with their booty, had yet been found. m. formery told him that, so far, the detectives had failed to find a single trace. guerchard said that he had three men at work on the search, and that he was hopeful of getting some news before long.

"the layman is impatient in these matters," said m. formery, with an indulgent smile. "but we have learnt to be patient, after long experience."

he proceeded to discuss with guerchard the new theories with which the discovery of the afternoon had filled his mind. none of them struck the duke as being of great value, and he listened to them with a somewhat absent-minded air. the coming examination of sonia weighed heavily on his spirit. guerchard answered only in monosyllables to the questions and suggestions thrown out by m. formery. it seemed to the duke that he paid very little attention to him, that his mind was still working hard on the solution of the mystery, seeking the missing facts which would bring him to the bottom of it. in the middle of one of m. formery's more elaborate dissertations the telephone bell rang.

guerchard rose hastily and went to it. they heard him say: "is that charmerace? ... i want the gardener.... out? when will he be back? ... tell him to ring me up at m. gournay-martin's house in paris the moment he gets back.... detective-inspector guerchard ... guerchard ... detective-inspector."

he turned to them with a frown, and said, "of course, since i want him, the confounded gardener has gone out for the day. still, it's of very little importance—a mere corroboration i wanted." and he went back to his seat and lighted another cigarette.

m. formery continued his dissertation. presently guerchard said, "you might go and see how victoire is, inspector—whether she shows any signs of waking. what did the doctor say?"

"the doctor said that she would not really be sensible and have her full wits about her much before ten o'clock to-night," said the inspector; but he went to examine her present condition.

m. formery proceeded to discuss the effects of different anesthetics. the others heard him with very little attention.

the inspector came back and reported that victoire showed no signs of awaking.

"well, then, m. formery, i think we might get on with the examination of mademoiselle kritchnoff," said guerchard. "will you go and fetch her, inspector?"

"really, i cannot conceive why you should worry that poor child," the duke protested, in a tone of some indignation.

"it seems to me hardly necessary," said m. formery.

"excuse me," said guerchard suavely, "but i attach considerable importance to it. it seems to me to be our bounden duty to question her fully. one never knows from what quarter light may come."

"oh, well, since you make such a point of it," said m. formery. "inspector, ask mademoiselle kritchnoff to come here. fetch her."

the inspector left the room.

guerchard looked at the duke with a faint air of uneasiness: "i think that we had better question mademoiselle kritchnoff by ourselves," he said.

m. formery looked at him and hesitated. then he said: "oh, yes, of course, by ourselves."

"certainly," said the duke, a trifle haughtily. and he rose and opened the door. he was just going through it when guerchard said sharply:

"your grace—"

the duke paid no attention to him. he shut the door quickly behind him and sprang swiftly up the stairs. he met the inspector coming down with sonia. barring their way for a moment he said, in his kindliest voice: "now you mustn't be frightened, mademoiselle sonia. all you have to do is to try to remember as clearly as you can the circumstances of the earlier thefts at charmerace. you mustn't let them confuse you."

"thank you, your grace, i will try and be as clear as i can," said sonia; and she gave him an eloquent glance, full of gratitude for the warning; and went down the stairs with firm steps.

the duke went on up the stairs, and knocked softly at the door of m. gournay-martin's bedroom. there was no answer to his knock, and he quietly opened the door and looked in. overcome by his misfortunes, the millionaire had sunk into a profound sleep and was snoring softly. the duke stepped inside the room, left the door open a couple of inches, drew a chair to it, and sat down watching the staircase through the opening of the door.

he sat frowning, with a look of profound pity on his face. once the suspense grew too much for him. he rose and walked up and down the room. his well-bred calm seemed to have deserted him. he muttered curses on guerchard, m. formery, and the whole french criminal system, very softly, under his breath. his face was distorted to a mask of fury; and once he wiped the little beads of sweat from his forehead with his handkerchief. then he recovered himself, sat down in the chair, and resumed his watch on the stairs.

at last, at the end of half an hour, which had seemed to him months long, he heard voices. the drawing-room door shut, and there were footsteps on the stairs. the inspector and sonia came into view.

he waited till they were at the top of the stairs: then he came out of the room, with his most careless air, and said: "well, mademoiselle sonia, i hope you did not find it so very dreadful, after all."

she was very pale, and there were undried tears on her cheeks. "it was horrible," she said faintly. "horrible. m. formery was all right—he believed me; but that horrible detective would not believe a word i said. he confused me. i hardly knew what i was saying."

the duke ground his teeth softly. "never mind, it's over now. you had better lie down and rest. i will tell one of the servants to bring you up a glass of wine."

he walked with her to the door of her room, and said: "try to sleep—sleep away the unpleasant memory."

she went into her room, and the duke went downstairs and told the butler to take a glass of champagne up to her. then he went upstairs to the drawing-room. m. formery was at the table writing. guerchard stood beside him. he handed what he had written to guerchard, and, with a smile of satisfaction, guerchard folded the paper and put it in his pocket.

"well, m. formery, did mademoiselle kritchnoff throw any fresh light on this mystery?" said the duke, in a tone of faint contempt.

"no—in fact she convinced me that she knew nothing whatever about it. m. guerchard seems to entertain a different opinion. but i think that even he is convinced that mademoiselle kritchnoff is not a friend of arsene lupin."

"oh, well, perhaps she isn't. but there's no telling," said guerchard slowly.

"arsene lupin?" cried the duke. "surely you never thought that mademoiselle kritchnoff had anything to do with arsene lupin?"

"i never thought so," said m. formery. "but when one has a fixed idea ... well, one has a fixed idea." he shrugged his shoulders, and looked at guerchard with contemptuous eyes.

the duke laughed, an unaffected ringing laugh, but not a pleasant one: "it's absurd!" he cried.

"there are always those thefts," said guerchard, with a nettled air.

"you have nothing to go upon," said m. formery. "what if she did enter the service of mademoiselle gournay-martin just before the thefts began? besides, after this lapse of time, if she had committed the thefts, you'd find it a job to bring them home to her. it's not a job worth your doing, anyhow—it's a job for an ordinary detective, guerchard."

"there's always the pendant," said guerchard. "i am convinced that that pendant is in the house."

"oh, that stupid pendant! i wish i'd never given it to mademoiselle gournay-martin," said the duke lightly.

"i have a feeling that if i could lay my hand on that pendant—if i could find who has it, i should have the key to this mystery."

"the devil you would!" said the duke softly. "that is odd. it is the oddest thing about this business i've heard yet."

"i have that feeling—i have that feeling," said guerchard quietly.

the duke smiled.