hetherwick went away from the sordid atmosphere of fligwood's rents wondering more than ever at this new development; he continued to wonder and to speculate all the rest of that day and most of the next. that granett's sudden death had followed on hannaford's seemed to him a sure proof that there was more behind this mystery than anybody had so far conceived of. personally, he had not the slightest doubt that whoever poisoned hannaford had also poisoned granett. and he was not at all surprised when, late in the afternoon of the day following upon that of the visit to dorking, matherfield walked into his chambers with a face full of news.

"i know what you're going to tell me, matherfield," said hetherwick, motioning his visitor to an easy chair. "the doctors have held a post-mortem on granett, and they find that he was poisoned."

matherfield's face fell; he was robbed of his chance of a dramatic announcement.

"well, and that's just what i was going to tell you," he answered. "that's what they do say. same doctors that performed the autopsy on hannaford. doesn't surprise you?"

"not in the least," replied hetherwick. "i expected it. they're sure of it?"

"dead certain! but, as in hannaford's case, they're not certain of the particular poison used. however—also as in his case—they've submitted the whole case to two big swells in that line, one of 'em the man that's always employed by the home office in these affairs, and the other that famous specialist at st. martha's hospital—i forget his name. they'll get to work; they're at work on the hannaford case now. difficult job, i understand—some very subtle poison, probably little known. however, i believe we've got a clue about it."

"a clue—about the poison?" exclaimed hetherwick. "what clue?"

"well, this," answered matherfield. "after you'd gone away from fligwood's rents yesterday afternoon, and while i was making arrangements for the removal of the poor chap's body, i took another careful look round the room. now, if you noticed things as closely as all that, you may have observed that granett's bed was partly in a sort of alcove—the head part. in the corner of that alcove, or recess, just where he could have set them down by reaching his arm out of bed, i found a bottle and a glass tumbler. the bottle was an ordinary medicine bottle—not a very big one. it had the cork in it and about an inch of fluid, which, on taking out the cork, i found to be whisky, and, i should say by the smell, whisky of very good quality. but i noticed that there was the very slightest trace of some sort of sediment at the bottom. there was a trace of similar sediment in the bottom of the tumbler. now, of course, i put these things up most carefully, sealed them, and handed them over to the doctors. for it was very evident to me—reconstructing things, you know—that granett had mixed himself a drink, a nightcap, if you like to call it so, from that bottle on getting into bed, and then had put bottle and glass down by his bed-head, in the corner. and just as i mean to trace that five-pound note, mr. hetherwick, so i mean to trace that bottle!"

"how?" asked hetherwick, closely interested. "and to what, or whom?"

"to the chemists where it came from," answered matherfield. "it came from some chemist's, and i'll find which!"

"there are hundreds of chemists in london," said hetherwick. "it's a stiff proposition."

"it's going to be done, anyway," asserted matherfield. "and it mayn't be such a stiff job as it at first looks to be. see here! there were labels on that bottle, both of 'em torn and defaced, it's true, but still with enough on them to narrow down the field of inquiry. i've had the face of the bottle photographed—here's a print of the result."

he brought out a photographic print, roughly finished and mounted on a card, and handed it over to hetherwick, who took it to the light and examined it carefully. it showed the front of the medicine bottle, with a label at the top and another at the bottom. each had been torn, as if to obliterate names and addresses, but a good deal of the lettering was left.

+-----------------------------+

| c. a , esq., |

| the mix re as before |

| no. a.1152 |

+-----------------------------+

+-----------------------------+

| _note_.--this medicine has |

| been dispensed by a fully |

| qualified chemist with the |

| to possible drugs |

| is guaranteed |

| wishes of |

| the pres- |

| |

| m.p.s. |

| st. w.c. |

+-----------------------------+

"that bottom label's the thing, mr. hetherwick," remarked matherfield. "let me get that hiatus filled up with the name and address of the chemist, and i'll soon find out who c. a. blank, esquire, is! the chemist is one in the west central district; he's a member of the pharmaceutical society; he'll have somebody whose initials are c. a. on his books; he'll recognise the number a.1152 of the prescription. it's a decided clue; and even if there are, as there undoubtedly are, scores of chemists in the west central district, i'll run this one down!"

hetherwick handed back the photograph and began to pace up and down the room. suddenly he turned on his visitor, his mind made up to tell him what he himself had been doing.

"matherfield," he said, dropping into his chair again and adopting a tone of confidence, "what do you make of this? i mean—what's your theory? is it your opinion that the deaths of these two men are—so to speak—all of a piece?"

"that is my opinion!" answered matherfield with an emphatic nod. "i've no more doubt about it than i have that i see you, mr. hetherwick. all of a piece, to be sure! whoever poisoned hannaford poisoned granett! i'll tell you how i've figured it out since the doctors told me, only a couple of hours since, what their opinion is about granett. this way: hannaford and granett knew each other at sellithwaite ten years ago. that night when granett left appleyard in horseferry road and turned into victoria street, he met hannaford—accidentally."

"why accidentally?" asked hetherwick.

"well, that's what i think," said matherfield. "i've figured in that way. of course, it may have been by appointment. but anyway, they met—we know that. now then, where did they spend their time between then and the time they got into your carriage at st. james's park? we don't know. but here comes in an unknown factor—what about the strange man at victoria, the man muffled to his eyes? two things suggest themselves to me, mr. hetherwick. did hannaford take granett to see that man, or did hannaford and granett meet at that man's? for i think that man, whoever he is, is at the bottom of every thing."

"why should they meet at that man's?" asked hetherwick.

"well," answered matherfield, "i think that secret of hannaford's has something to do with it. he had the sealed packet on him when he left malter's hotel; it had disappeared when we searched his clothing after his death. now, the granddaughter says it had to do with chemicals. suppose the tall, muffled man was a chap whose business opinion on this secret hannaford wanted, and that they met at victoria and went to the man's rooms somewhere in that district? suppose granett—another man in the chemistry line—came there, knowing both? supposing the muffled man poisoned both of 'em, to keep the secret to himself? do you see what i'm after? very well! there you are. the thing is to hunt out that man, whoever he is. i wish i knew what hannaford's secret was, though—its precise nature."

"matherfield," said hetherwick, "i'll tell you! you've been very confidential with me; i'll be equally so with you, on condition that we work together from this. the fact is, i've been at work. i'm immensely interested in this case. ever since i saw hannaford die in that train and in that awfully mysterious fashion it's fascinated me, and i'm going to the very end of it. now i'll tell you all i've been doing, and what i've discovered. listen carefully."

he went on to tell his visitor the whole details of his visit to sellithwaite, of the results of his investigations there, and of rhona's doings and observations at riversreade court. matherfield listened in absorbed silence.

"is miss hannaford going to this secretaryship, then?" he demanded abruptly, at the end of hetherwick's story. "is it settled?"

"practically, yes," replied hetherwick. "i heard from lady riversreade this morning; so did mr. kenthwaite. we gave miss hannaford—to be known to lady riversreade as miss featherstone—very good recommendations for the post, and i expect that as soon as she's had our letters, lady riversreade will telephone to miss hannaford that she's to go at once. then—she'll go."

"to act as—spy?" suggested matherfield.

"if you put it that way, yes," assented hetherwick. "though, from what she saw of her yesterday, miss hannaford formed a very favourable opinion of lady riversreade. however, i'm so certain that somehow or other, perhaps innocently, she's connected with this affair, that we mustn't lose any chance."

"and miss hannaford will report anything likely to you?" asked matherfield.

"just so! miss hannaford's duties don't include any sunday work; on sunday she'll come to town, and if there's anything to tell, she'll tell it—to me. she's a smart, clever girl, matherfield, and she'll keep her eyes open."

matherfield nodded, and for a while sat silent, evidently lost in his own thoughts.

"oh, she's a clever girl, right enough!" he said suddenly. "um! i wonder who this lady riversreade really is, now?"

"this lady riversreade!" laughed hetherwick. "a multi-millionairess!"

"aye, just so; but who was she before her marriage? if she is the woman who was known as mrs. whittingham——"

"can there be any doubt about it after what i found out?"

"you never know, mr. hetherwick! lord bless you! they talk about the long arm of coincidence. why, in my time i've known of things that make me feel there's nothing wonderful about the most amazing coincidence! but—if lady riversreade used to be mrs. whittingham, then i'd like to know all about mrs. whittingham until she became lady riversreade, and who she was before she was mrs. whittingham, if she ever was mrs. whittingham!"

"stiff job, matherfield," said hetherwick. "i think we shall have enough to do to keep an eye on lady riversreade."

"you anticipate something there?" suggested matherfield.

"i think something may transpire," replied hetherwick.

matherfield got to his feet.

"well," he said, "keep me informed, and i'll keep you informed. we've something to go on—lord knows what we shall make out of it!"

"you're doing your best to trace the tall man?" asked hetherwick.

"best!" exclaimed matherfield with an air of disgust. "we've done our best and our better than best! i've had special men all round that victoria district; i should think every tall man in that part's been eyed over. and i believe that mr. ledbitter has so got the thing on his brain that he's been spending all his spare time patrolling the neighbourhood and going in and out of restaurants and saloons looking for the man he saw—of course, without result!"

"all the same," said hetherwick, "that man is—somewhere!"

matherfield went away, and except at the inquest on granett—whereat nothing transpired which was not already known—hetherwick did not see him again for several days. he himself progressed no further in his investigations during that time. rhona hannaford betook herself to riversreade court, as secretary to its mistress's home, and until the sunday succeeding his departure hetherwick heard nothing of her. then she came up to town on the sunday morning and, in accordance with their previous arrangement, hetherwick met her at victoria, and took her to lunch at a neighbouring hotel.

"anything to tell?" he asked, when they had settled down to their soup. "any happenings?"

"nothing!" answered rhona. "everything exceedingly proper, business-like, and orderly. and lady riversreade appears to me to be a model sort of person—her devotion to that home and its inmates is remarkable! i don't believe anything's going to happen, or that i shall ever have anything to report."

"well, that'll have its compensations," said hetherwick. "leave us all the more time for ourselves, won't it?"

he gave her a look to which rhona responded, shyly but unmistakably; she knew, as well as he did, that they were getting fond of each other's society. and they continued to meet on sundays, and three or four went by, and still she had nothing to tell that related to the mystery of hannaford and granett.

three weeks elapsed before matherfield had anything to tell, either. then he walked into hetherwick's chambers one morning with news in his face.

"traced it!" he said. "knew i should! that five-pound note—brand new. only a question of time to do that, of course."

"well?" inquired hetherwick.

"it was one of twenty fivers paid by the cashier of the london and country bank in piccadilly to the secretary of vivian's," continued matherfield. "date—day before hannaford's death. vivian's, let me tell you, is a swell night club. now then, how did that note get into the hands of granett? that's going to be a stiff 'un!"

"so stiff that i'm afraid you mustn't ask me to go in at it," agreed hetherwick good-humouredly. "i must stick to my own line—when the chance comes."

the chance came on the following sunday, when, in pursuance of now established custom, he met rhona. she gave him a significant look as soon as she got out of the train.

"news—at last!" she said, as they turned up the platform. "something's happened—but what it means i don't know."