quite unconscious that his most dangerous enemies were so near, anstruther carefully selected a cigarette and lighted it. he proceeded then to make a careful examination of the pile of posters at his feet, and smiled his approval. "very good, very good indeed; those hands stand out beautifully. within a week's time from now the message will have been carried from london to st. petersburg and from paris to constantinople. the men i am after cannot get away from me. whatever great capital they are in, that poster confronts their eyes like an avenging conscience. then they realize their helplessness and bow to the inevitable. you may doubt me if you like; but i tell you that this scheme is absolutely sure and safe."

"provided that we have the money to carry it out," the man behind the lantern grunted. "don't forget that. clever as you are, you can't make money by merely holding up your little finger. you promised us a thousand pounds when we had finished our part of the bargain, and that was completed a month ago. of course, you have got the cash in your pocket?"

a frown of annoyance crossed anstruther's face. there was a clenching of his hands not unlike that depicted by the poster of the mysterious nostalgo; he made a half step forward; then he seemed to get himself in hand again, and smiled carelessly. "as a matter of fact, i have not the money in my pocket. things are not going quite as well lately as i could have wished, but it is only a matter of a day or two anyway; nay, it is only a matter of hours. is the woman here?"

the man behind the lantern sulkily declared that he knew nothing about the woman, and cared less. he asked pointedly whether they were to expect mr. carrington that evening, and, if so, whether his visit was likely to be attended with substantial results.

"i tell you i don't know," anstruther said angrily. "i told him to be here at eleven o'clock, but i suppose he has funked it. but the woman is a very different matter. jacob, go into the back room and bring her in here."

"not i," the man addressed as jacob replied. "i don't forget the last time we met. she may be milk and honey to you, but she is prussic acid as far as i am concerned."

anstruther stepped to the doorway and whistled softly. it might have been a call given to a well-broken dog, so careless and contemptuous was it. indeed, anstruther did not wait to see the result of his summons, but returned to the room with the easy assurance of a man who knows that his lightest call will be obeyed.

almost immediately the two watchers standing on the landing were conscious of a shadowy form passing close to them. they had no time to shrink back, they had not even time for surprise, when a light hand was laid on the arm of each and an eager voice began to whisper in their ears.

"rash to the verge of madness," the melancholy voice said sadly. "i warned you not to come--i implored you not to take a hand in this business. i could have settled it all for you if you had left it all to me; but youth ever will be served. won't you go away even now and leave it all to me?"

there was something so pitifully imploring in the speech that the listeners thrilled in sympathy. from the first word they had no difficulty in guessing the identity of the speaker. it was none other than serena who was addressing them in those despairing accents.

"i am afraid you are too late, serena," jack said. "besides, we have some one else to consider in the business. it is possible that your efforts may be successful as far as we are concerned; but we have discovered to-night that anstruther is plotting against the happiness of many people who are as innocent as ourselves. i tell you, we must see this thing through now. but why stay here, why linger, when your tardiness is likely to increase our trouble?"

at this point anstruther advanced towards the door and whistled again, this time more sharply. with a sigh of deep regret serena walked forward and entered the room. in the bright light of the apartment her face looked paler and more dejected than usual. though jack had seen for himself the volcano of passion and emotion of which serena was capable when not under the influence of her employer, he could not fail to notice how tame and frightened she appeared to be now. it was as if anstruther possessed something like a power over her. her dark eyes seemed mechanically to follow his every movement; he had only to raise his hand and her look followed it.

"so you have come at last," anstruther said. "how long have you been in the house?"

"i came as soon as you told me, master," serena murmured, like one who talks in her sleep. all will power seemed to have gone out of her for the moment. "what would you have of me to-night?"

anstruther replied harshly that serena must know perfectly well what was required of her. nevertheless he proceeded to detail his instructions, which were still unfinished when another footstep was heard upon the stairs and a newcomer entered. the two watchers outside were not in the least surprised at the pale, somewhat conceited features of the violinist padini; indeed, they were past all surprises now. padini had bowed with an air of exaggerated politeness to serena.

"ha, ha, my coy fascinator," he cried, "so i am not to be deprived of the pleasure of your company. i am not likely to soon forget the enchanting evening we spent together chez carrington. i am sorry to be late, anstruther, but the fact is, your english audiences are not so cold as i had first imagined. positively they would not let me off with less than four encores. ma foi,you must have had the full value of your money in your chamber music to-night. a rare treat for miss helmsley; doubtless she has noticed the marvelous improvement made by her guardian in his playing of late."

the violinist chuckled as if in the enjoyment of an exquisite joke. serena flashed him a glance of bitter hatred and contempt.

"i should like to know the meaning of this," rigby whispered. "i suppose it refers in some way to the mysterious music which you told me about last night. do you think it possible that serena could enlighten us on this point as she appears to know all about it? if not, why does she look at padini in that scornful way?"

any further signs of enjoyment on the part of padini were cut short by an impatient oath from anstruther.

"that is mere child's play," he exclaimed. "very clever and all that kind of thing, but an intelligent schoolboy might have done as well."

jack intimated in a whisper to rigby that he himself stood in the position of the said intelligent schoolboy. he had a pretty shrewd idea how the thing had been managed, and to what purpose; but there would be time enough to explain all that presently. what they had to do now was to stay as long as possible, and gather all they could from a careful study of the proceedings taking place in the room. it was anstruther who first broke the silence.

"are we going to stand fooling here all night?" he exclaimed angrily. "padini, get that exaggerated fur coat of yours off, and make yourself up to look like an english gentleman as far as possible. you will find everything necessary in the room at the back of the house. the same remark applies to you, serena. my word! to think that a woman so pale, so haggard, as you are now can make up to look like eighteen and possess the beauty of diana! what a pity it was you ever left the stage!"

the woman's face flushed angrily. there was a nervous tension about her to-night that anstruther had never noticed before. was she going to be defiant? he asked. did she understand what she was doing when she proposed to measure her strength against his? but the flame still raged on serena's hot cheeks, and her lips were still hard and mutinous.

"take care you do not drive me too far," she whispered hoarsely. "a cat is a harmless creature enough, but i read once of a cat that turned upon a man and killed him. you dare to taunt me with my past. when i think of what that past might have been but for you, i declare that i could find it in my heart to kill you. i am so weak and timid, you are so strong and brave; and yet even you must sleep at times, and a man asleep is as harmless as a babe. a spot of gray powder, a drop of liquid no larger than a pin's point placed between your teeth, and the career of spencer anstruther is finished."

the words were uttered with such dramatic force and intensity that even anstruther refrained from smiling. it seemed to the listeners outside that here was a great genius lost to the stage.

"i should not care to encounter that woman's hostility," rigby murmured. "look at the intense expression of her face. but, really, i hope she is not going to defy him to-night. if she does we are likely to have trouble for our pains."

but serena's outbreak of passionate anger was over as swiftly as an april shower. she looked up in the face of her master as a dog might do that had been convicted of theft. anstruther smiled with the air of a man who merely tolerates a passing anger of a fellow creature. it was as if he had caged this woman so that he could watch her passions and emotions as a naturalist studies the habits and ways of loathsome insects.

"i suppose you must give vent to your feelings sometimes," he said. "and now that you have had a little fling we had better get on with our business. you will go with padini to-night to----"

"no, no!" serena cried. "i implore you to spare me that humiliation again. what have i done that i should have to endure all this--what can be possibly gained by it?"

for the first time anstruther displayed real signs of anger. "now, listen to me," he said. "once for all, i tell you not to speak to me like this again. do you think i have studied you all these years for nothing? do you suppose i do not know how disloyal you are in your heart towards me? there is one class of woman who has to be ruled by fear alone, and you are one of them. you will do to-night what i ask you, not merely to-night, but by months and years, in and out, it will be for me to order and you to obey. and, whilst we are on the subject you are to say nothing further than you have already said to mr. masefield. you understand what i mean?"

it was quite evident that serena understood the full significance of anstruther's speech. pale as her face had been before, it turned now to a still more deathly pallor. she essayed to speak, but her lips refused the office.

"i don't quite follow you," she managed to stammer out at length. "if you accuse me of disloyalty----"

anstruther intimated that that was exactly what he did mean. it was rather an uncomfortable moment for jack, listening there. he was beginning to fully realize the marvelous cunning of the man with whom he had to deal. he wondered how it was possible for anstruther to discover the gist of his conversation with serena that afternoon. he was saying something of this in a whisper to rigby when padini returned to the room. the violinist was dressed now exactly as he had been attired two nights before when jack had seen him at carrington's chambers. his jaunty air for the moment had vanished; he looked suspicious and uneasy. anstruther's keen eye noticed this as it noticed everything.

"now, what's the matter?" he asked. "have you seen a ghost or something equally terrible?"

"no, i haven't," padini replied sulkily. "but lam pretty sure there is somebody in the house. i am ready to swear that i saw the shadow of a man moving on the landing outside."

with a contemptuous smile anstruther walked towards the door. there was perhaps no immediate danger for the listeners, seeing that anstruther evidently attached no importance to padini's statement; but it was just as well to be on the safe side. rigby slipped quietly into a doorway leading to a bedroom and dragged jack in after him. then he closed the door very gently and waited for further developments. he had not long to wait, for almost immediately there was a click of the latch, and anstruther's receding footsteps melted into silence.

"well, that sets your mind at ease," anstruther was heard to say. "if there are any birds here, i have them safely caged."

with a feeling of apprehension, rigby laid his hand on the door-knob. his worst fears were absolutely realized. he and jack had been locked in the room.