bates was sitting up in bed nursing an aching head, and plotting out schemes whereby he could best retrieve the disaster of the previous night. it was fortunate for the inspector that one of carrington's night watchmen should have heard something of the disturbance on the previous night, and come hotfoot to his assistance. there was no great damage done beyond a bruised face and a general shock to the system. bates felt all the better for a good night's rest, and was quite ready now to carry on the campaign against his powerful foe. it was some time in the afternoon before jack masefield put in an appearance at bates's lodgings, having been summoned there by a special messenger. jack smiled as he noticed bates's somewhat dilapidated condition.

"what's the matter?" he asked. "you do not seem to have been as successful as you might--i mean over last night's business. was the thing a failure, or were you satisfied?"

bates explained that up to now the battle was a drawn one. he had a feeling that jack would be able to help him, and that was why he asked him to call this afternoon.

"i am not in the least dissatisfied with my last night's work," he explained. "in the first place, we have carrington absolutely at our mercy. i let him know what we have discovered, and he will do anything for us that we desire. after that, i played the part of the mythical maggs, and in due course disclosed myself to mr. anstruther. perhaps i was a little too confident; anyway, i gave him a chance to murder me, and he responded to the opportunity with absolute enthusiasm. but for the opportune arrival of the night watchman, scotland yard would have lost one of its most distinguished ornaments. it was a very near thing, i assure you."

"but what could he possibly gain by that?" jack asked.

"well, you see, i had let him know that i was quite alone in the business," said bates. "at the same time, he was not aware that my information was so complete. if he could murder me and get safe home without being detected, he was in a position to prove an absolute alibi. of course, i did not dream that i was running any risk of my life--but that is not the point. you will remember my suggesting to you yesterday the advisability of you dining in panton square last night. i suppose that was all right?"

jack replied that he had followed bates's instructions out implicitly. he had done all he could in that way.

"very well, then. you see what i am driving at. i take it for granted that anstruther's mysterious musical friend was much in evidence last night. i have no doubt that miss helmsley and yourself listened with rapt attention to the music in the study."

"we had every opportunity of doing so," jack said.

"that is precisely what i expected. anstruther must have left the house a little after ten o'clock, and i don't see how it was possible for him to return much before half-past twelve. i suppose you didn't happen to see him when he came in?"

"indeed i did," jack said. "it was quite half-past twelve when i was leaving the house. the music was still in progress, but when i slipped out of the front door, anstruther was rapidly approaching the house running across the lawn. he seemed very much annoyed and put out when he saw me, and muttered something to the effect that he had heard somebody trying the front door. i understood him to say that he had not been out all the evening, but that was all nonsense. i could see by his boots that he had been walking some considerable distance. of course, you see what the dodge is: he does not leave the house by the door, but by the french window leading from the study to the garden. this window he leaves unfastened, so that he can get back at any time without a soul being any the wiser. of course, there was always a chance of somebody finding the window unlatched, but that is a small matter."

"is the window always left open?" bates asked thoughtfully.

jack replied that he thought so. bates smiled with the air of a man who is perfectly well satisfied.

"i am going to get up presently," he said. "after i have had a bath and some tea, i shall be quite fit for duty again. i want you to find some pretext for calling at anstruther's just after dinner, because i may need your assistance."

"what are you going to do?" jack asked eagerly.

"well, in the first place i am going to arrest mr. anstruther," bates replied. "in the second instance, i have another little scheme, which we need not discuss now. i want you to go as far as mr. rigby's chambers and get him to keep an eye on padini, and see that last night's programme is repeated, if possible. this is rather an important thing. i think i can trust mr. rigby to manage it."

jack went off obediently enough, and subsequently ran rigby to earth at the offices of the planet. the latter seemed delighted at the turn which affairs were taking. he began to see now that he would be able to carry out for his paper the series of sensational articles required by the proprietor. "we shall have a splendid scoop," he said. "indeed, one might almost make a three-volume novel out of it. i am only too sorry that i can't be at anstruther's to-night and witness the arrest. i shall leave you to supply all the graphic details. i can easily manage the padini business this evening by writing to the fellow that i have a check to pay over and shall call at his rooms late to-night. i am sure to find him there. he is very hard up, and the money is certain to fetch him."

"there are other things connected with this business," jack said, "which puzzle me. for instance, there is that affair of the mysterious mr. ferris, whose acquaintance i made at the great metropolitan hotel. i am quite sure, also, that seymour has some deep design on hand. you may be absolutely certain that that business of the crystal ball played off on anstruther at lady barmouth's dance the other night was not mere flummery."

rigby was of the same opinion. he was anxious to know if anything had been yet done in the matter of carrington's private safe and the service of cellini plate which anstruther had coolly appropriated for himself. but on this point jack had no information to offer. he did not doubt that the whole thing would be explained in a few hours now. he killed the day as best he could, and after dinner turned his steps in the direction of panton square. mr. anstruther and miss helmsley had practically finished, serena explained, but they had not yet left the dining-room. anstruther raised his brows significantly as jack entered the dining-room, but his manner was polite and cordial enough as he invited the visitor to a seat and a glass of claret. he did not look in the least perturbed or put out; on the contrary, jack had seldom seen him so easy and self-possessed. his neuralgia was quite gone. he had charmed it away as usual, he said with the soothing aid of music.

"how is it you never bring your violin up to the drawing-room?" claire asked. "we hardly ever have any duets together."

"after next week," anstruther promised. "really, i am a great deal more busy than i appear to be, and i feel it quite easy to play and think at the same time."

jack glanced across the table significantly at claire, and she seemed to divine what he was thinking about.

"i thought i knew most of your music," she said , "but there was one little item last night that took my fancy immensely. i feel quite sure that you composed it yourself."

anstruther disclaimed any such gift. fond as he was of his violin, it had never occurred to him to try his hand at original composition.

"all the same, i really must get it," claire persisted. "i am sorry that you do not recall the piece at all. if you will come into the drawing-room with me, and can spare me a few minutes, i will strum the piece over to you. it so fascinated me that i committed it to memory. do come along for a moment."

anstruther laughed, as jack thought, rather uneasily. he tried skilfully enough to divert the conversation into another channel, but claire's enthusiasm refused to be baffled. anstruther's face darkened for a moment, and there was a look in his eyes that boded ill to somebody. he rose and walked across towards the door, and up the stairs in the direction of the drawing-room..

"very well, if you must," he said. "i can give you ten minutes. i dare say it is some silly trifle that i have heard somewhere without recognizing its source."

claire seated herself at the piano, and played the little piece off with both brilliancy and feeling. as a matter of fact, she had been practicing it several times during the afternoon until she had it absolutely correct. the slow, mournful chords died away at length, and then claire turned to her guardian with a smile.

"that is it," she said . "that is the little piece that so fascinated me last night. surely you can tell me the name of it and where it came from?"

the question was apparently simple enough, but anstruther appeared to be absolutely incapable of answering it.

"do you mean to say you could forget a thing like that?" claire protested. "it seems to me impossible."

"perhaps it made less impression upon me than it did you," anstruther muttered. "i haven't the slightest recollection of playing it myself. in fact----"

anstruther broke off in absolute confusion. the incident, trivial as it seemed, had upset him altogether. he was about to betray himself by saying that he had never heard the piece before, and that it had no place amongst his music; but he pulled himself up just in time. he bitterly blamed padini's carelessness. it was no part of the programme for his double to give him anything but pieces of music with which he was absolutely familiar. what he might have said and done was frustrated by the appearance of serena, who announced that a gentleman down-stairs desired to see mr. anstruther.

jack felt his pulses beating a little faster, for he had had no reason to inquire who the stranger was. serena's eyes were demure and downcast as usual as she replied to anstruther's question that the gentleman down-stairs was none other than inspector bates, of scotland yard. only just for an instant did anstruther falter and turn pale, then he was absolutely himself again. he almost wished now that he had not waited so long. he had his ingenious alibi, it was true, but even that might fail. there were so many meshes in the nets of scotland yard. in a calm, even voice he ordered serena to show the stranger up-stairs. bates came at length, a little pallid and bruised, but otherwise little worse for his last night's adventure.

"and what might be your business with me, inspector?" anstruther asked. "it is some time since i had the pleasure of meeting you. will you please take a seat?"

"i do not see the necessity," bates responded. "as my business is private, perhaps you will be good enough to follow me to your study. i will speak if you like, but----"

"you may say anything you please," anstruther said defiantly.

"then i arrest you on a warrant, charging you with attempted burglary last night," bates said pithily. "you were on the premises belonging to the city and provincial bank with a felonious intent of breaking into a safe between the hours of eleven and half-past twelve. need i say any more?"

"amazing," anstruther laughed. "fortunately i have my witnesses at hand to prove that i was not off these premises during the hours you mentioned. as a matter of fact, i was in my study playing my violin all the time."

"sounds ingenious," bates muttered, "but in these days of clever mechanical contrivances--by the way, is not some one playing the violin down-stairs now?"

despite his command of himself, a furious curse broke from anstruther's lips. for even as bates spoke, there came sounds of liquid melody from the study. not only was this so, but, furthermore, the piece in question was precisely the same as the one that claire had just been playing over to her guardian. the girl rose to her feet, and looked across at jack significantly. bates smiled in the manner of one who has solved a great problem.

"really, a most remarkable coincidence," he said. "i am afraid this rather spoils the simple beauty of your alibi, mr. anstruther; unless, perhaps, you have some friend who entertains your household at such times as business calls you elsewhere. but let us go down-stairs and see for ourselves."

"no, no," anstruther cried furiously. "you shall not do it. you shall not interfere. i'll kill you first."

"come along," bates responded. "come with me and witness the solving of the mysterious problem."