claire sat there, her mind half on her music and half on the extraordinary conduct of her lover. not that she did not trust him implicitly; but, still, it seemed strange that he should have gone off without explaining the cause of his agitation.

some one next to her touched her on the elbow and asked a question as to an item on the programme. the question was repeated twice before claire realized that she would have to pull herself together. she replied quite at random; then she looked about her, and became cognizant of the fact that padini was still on the stage, bowing his acknowledgments of the thunderous applause which had greeted his magnificent efforts.

yet a closer glance did not serve to show claire anything sinister in the artist's personality. he was pale and clean-shaven, palpably very nervous, and yet pleased with the warmth of his reception. surely there could have been no mystery connected with a man like this.

on the other hand, the marvelous likeness between his playing and the execution in the same piece displayed by anstruther two nights ago could not possibly be overlooked by any one professing to any musical knowledge at all. claire hoped that the inevitable encore would produce a repetition of the same piece.

surely enough, padini came forward and struck the opening bars of the same rhapsodie. with eyes closed and mind eagerly concentrated on the music, claire followed every passage with rapt attention. there was no longer any possibility of mistake. the padini interpretation of the piece was exactly that of anstruther. was anstruther, therefore, a consummate master of his art or a showy humbug or charlatan? could it have been possible that this new artist had been concealed in the panton square library two nights before? but, on the face of it, this was absolutely impossible. padini had only been in england a little over eight and forty hours, and his first appearance in london had been at a musical "at home" on the same night that anstruther had played the nocturne in panton square.

claire was still debating this problem in her mind when jack returned to his seat. he looked a little pale and shaky, but the grim smile on his face was determined enough. "my dearest girl, i am going to ask you a little favor," jack whispered. "i hope you won't think it the least rude of me, but i want you to excuse me going back with you. can't you guess that there is something more than meets the eye here?"

"i should be very blind indeed if i did not," claire replied. "jack, what is the meaning of this strange mystery? either signor padini was at our house the other night, or my guardian learned to play that rhapsodie after having had lessons from the man on the platform before us."

"i may be wrong, of course," jack said, "but i feel pretty sure that i have guessed the problem. that is why i want you to go off by yourself, and leave me to play the detective so far as padini is concerned. it is not altogether a pleasant job, but i am going to follow that fellow when he leaves the hall."

so saying, jack rose from his seat, and claire obediently followed his example. once outside, jack called a cab, and gave the driver his instructions.

"i think that will be all right," he said. "you may expect me to come round after dinner, my darling girl. i hope you are not in the least annoyed with me; but there is danger ahead for you and me, and it is my duty to prevent it at all hazards. i declare if i had not almost forgotten one of the most important things i had to say to you. on no account are you to breathe a word of this afternoon's visit to your guardian. he is not to know that you have been with me or anybody else to the albert hall to-day."

claire glanced at the pale, anxious face of her lover and gave the desired assurance. she felt perfectly safe in his hands; he would tell her all there was to be told in due course; and now for the first time she congratulated herself on the fact that her engagement had been kept a secret from anstruther.

meanwhile jack had returned to the back of the hall. so far as he could recollect, padini was down on the programme for no further item that afternoon, therefore it was only a matter of waiting till the violinist emerged, and following him to his destination. but jack had succeeded in consuming three cigarettes without any sign of the artist rewarding his patience. taking half-a-crown from his pocket, he crossed the road and proceeded to interview the stage-door keeper.

"oh, that foreign-looking chap, is it?" the stage-door guardian said. "signor somebody or other who plays the fiddle. why, he's been gone the last ten minutes."

"gone!" jack exclaimed, with palpable dismay. "why, i have been watching most carefully for him the last half-hour. was he wrapped up or shawled in any way?"

whilst jack still stood arguing there a slim young man, with fair moustache turned upwards à la german emperor, passed and repassed him hurriedly. the stranger passed into a smartly appointed hansom and vanished.

"well, there's your man," the doorkeeper exclaimed. "he must have forgotten something and returned for it."

jack muttered his thanks, parted with his half-crown, and went into the roadway thoroughly puzzled. he could not for a moment doubt the word of the doorkeeper, who was naturally an expert in a recognition of faces. as a matter of fact, the man with the turned-up moustache was the same individual who had been so mysteriously concealed in panton square, and who had afterwards accompanied the deaf-mute girl to mr. carrington's. on the stage padini had appeared as a slight, slim man, whose face was absolutely devoid of hair.

jack stood thoughtfully in the middle of the road, wondering what to do next. his first idea was to go at once and look up rigby. he must have been standing there a great deal longer than he had imagined, for presently he saw the smart hansom return and take its place on the rank. here was a slice of luck indeed. jack crossed over and hailed the hansom.

"here, i want you to drive me to the office of the planet," he said. "i suppose you know where that is. do you want to earn an extra half-sovereign?"

"that's the way i was educated," said the cabman, with a grin. "oh, my last fare, is it? well, i can easily answer that question. gent with the cocked-up moustache. i have just driven him to 5, panton square."

jack stepped into the hansom, feeling that luck was entirely on his side. he knew now that he was on the track of something more than mere coincidence. for 5, panton square was no less a place than the residence of spencer anstruther, claire's guardian. here was proof positive that padini, the violinist, a perfect stranger to london, was at any rate on terms of friendship with anstruther. there was nothing for it now but to seek out rigby and tell him all that had happened without delay. rigby was found in his room at the planet office, mournfully drawing skeletons on a sheet of blotting-paper. he nodded thoughtfully as jack came in; then, catching sight of the latter's eager face, asked what was in the wind.

"i have been making discoveries galore," jack responded. "you would hardly expect me to do that through the medium of an afternoon concert; but there it is. you have heard of this new violinist, signor padini, i suppose?"

"oh, yes," rigby said indifferently. "well, a typical class of foreign boomster, i suppose."

"that is not the point," jack proceeded to explain. "you will recollect what i told you about the empty study in anstruther's house from which the music proceeded in that strange, unaccountable manner. naturally, i thought the player was anstruther himself--anstruther wonderfully improved or inspired beyond all recognition; but now i know that such was not the case. dick, there is something devilish in this strange business--the empty room, the unearthly music, the strange appearance of that young man with his deaf-mute companion, followed so closely by the death of nostalgo. what does it all mean?"

"i will give a thousand pounds to know," rigby responded.

"well, i think i can tell you," jack went on. "you will recollect the night before last, during our chance meeting at carrington's, that i asked you to keep an eye on a young man with moustache turned up à la german emperor. would you be surprised to hear that this young man was no less a person than signor padini?"

"impossible!" rigby exclaimed. "how could you prove such a statement?"

"well, i am going to prove it, anyway. together with miss helmsley i went to hear padini this afternoon. by some strange freak of fate he had chosen chopin's rhapsodie in f as his item on the programme. directly he began to play my mind went back to that strange, weird music in anstruther's study. it was not i alone who noticed this subtle resemblance; in fact, claire recognized it as soon as i did. mind you, every musician of note has his little tricks and fancies which are absolutely peculiar to himself. when i shut my eyes, i could literally hear padini playing in anstruther's house.

"i sent claire home in a cab, and proceeded to wait till padini left the albert hall. i missed him, of course, for padini was a clean-shaven man on the stage. as a matter of fact, he must be a very conceited creature, seeing that in private life he wears a fair moustache. i got that from the doorkeeper; but, what is more to the point, the cabman who drove me here is the same man who half-an-hour ago dropped padini at anstruther's house. now, i would like to know what you make of that."

rigby listened thoughtfully to all that jack had had to say. the significance of the revelations was not lost upon him.

"and yet, i dare say, anstruther would deny any knowledge of padini if you asked him," he said. "still, we know a great deal, and, clever as anstruther is, he cannot possibly conceive the fact that we are so closely acquainted with his movements. let's go and call upon the beggar, shall we? pretend that we want to consult him on some matter of business. anything will do. did you keep your cab?"

"well, yes; it occurred to me that we might want him again, and, besides, the driver can prove that he left padini at 5, panton square."

panton square was reached at length; the cabman had been discreetly dropped at the corner of the street. jack rang the bell, which was answered by serena. in the full light of the afternoon sunshine her strange, inscrutable face looked more haggard and strange than usual. there was the same furtive droop of her eyelids, the same pitiable shake of her hands, that suggested the beaten hound, that jack had so often noticed before. he would have given much, as a writer of stories himself, to have known the secret history of this woman. docile and tame as she appeared to be, she was still capable of passionate emotion, or the dilatation of her black pupils spoke falsely. though she was meek and friendly enough, there was ever a suggestion that she was on her guard.

"your master in?" rigby asked breezily. "but we know that he is. don't you trouble about us; we will go to the study ourselves."

serena stood there as if something gripped her throat and choked her utterance.

"but my master is not at home," she protested. "he has not been at home all day; neither do i know what time to expect him to-night. i fancy he is out of town altogether."

"that's rather awkward," rigby said. "we came here on business, expecting to meet a friend of ours. i suppose you have seen nothing of him--a tall, slim young man, with rather a fierce type of moustache?"

"there has been no visitor calling here to-day," serena replied, with the air of one who repeats a well-learned lesson. "i am the only servant in the house at present, and should have known if anybody had called."

jack did not dare to glance at his companion, feeling that those dark, interrogating eyes were fixed upon his face. a sudden impulse moved jack; he decided upon trying the effect of a swift surprise. he tapped the woman familiarly on the shoulder.

"come, come," he said, with a jocular ring in his voice. "do you mean to tell me that you have not had a visit to-day from signor padini?"

a stifled cry broke from the woman; she clenched her hands in an attitude of pain.