Elder and younger woman alike took Matherfield's intimation quietly. Rhona made no remark. But Mrs. Keeley spoke impulsively.  
"There never was a more popular man than he was—with everybody!" she exclaimed. "Who should want to take his life?"
 
"That's just what we've got to find out, ma'am," said Matherfield. "And I want to know as much as I can—-I dare say Miss Hannaford can tell me a lot. Now, let's see what we do know from what you told me this morning. Mr. Hannaford had been Superintendent of Police at Sellithwaite for some years. He had recently retired on his pension. He proposed to live in London, and you and he, Miss Hannaford, came to London to look for a suitable house, arrived three days ago, and put up at this hotel. That's all correct? Very good—now then, let me hear all about his movements during the last three days. What did he do? Where did he spend his time?"
 
"I can't tell you much," answered Rhona. "He was out most of the day, and generally by himself. I was only out with him twice—once when we went to do some shopping, another time when we called on Mr. Kenthwaite at his rooms in the Temple. I understood he was looking for a house—seeing house agents and so on. He was out morning, afternoon and evening."
 
"Did he never tell you anything about where he'd been, or whom he'd seen?"
 
"No. He was the sort of man who keeps things to himself. I have no idea where he went nor whom he saw."
 
"Didn't say anything about where he was going last night?"
 
"No. He only said that he was going out and that I should find him here when I got back from the theatre, to which I was going with Mrs. Keeley. We got back here soon after eleven. But he hadn't come in—as you know."
 
"You never heard him speak of having enemies?"
 
"I should think he hadn't an enemy in the world! He was a very kind man and very popular, even with the people he had to deal with as a police-superintendent."
 
"And I suppose he'd no financial worries—anything of that sort? Nor any other troubles—nothing to bother him?"
 
"I don't think he'd a care in the world," said Rhona confidently. "He was looking forward with real zest to settling down in London. And as to financial worries, he'd none. He was well off."
 
"Always a saving, careful man," remarked Mrs. Keeley. "Oh, yes, quite well off—apart from his pension."
 
Matherfield glanced at Hetherwick, who had listened carefully to all that was asked and answered. Something in the glance seemed to invite him to take a hand.
 
"This occurs to me," said Hetherwick. He turned to Rhona. "Apart from this house-hunting, do you know whether your grandfather had any business affair in hand in London? What I'm thinking of is this—from what I saw of him in the train, he appeared to be an active, energetic man, not the sort of man who, because he'd retired, would sit down in absolute idleness. Do you know of anything that he thought of undertaking—any business he thought of joining?"
 
Rhona considered this question for a while.
 
"Not any business," she replied at last. "But there is something that may have to do with what you suggest. My grandfather had a hobby. He experimented in his spare time."
 
"What in?" asked Hetherwick. Then he suddenly remembered the stained fingers that he had noticed on the hands of both men the night before. "Was it chemicals?" he added quickly.
 
"Yes, in chemicals," she answered with a look of surprise. "How did you know that?"
 
"I noticed that his hands and fingers were stained," replied Hetherwick. "So were those of the man he was with. Well—but this something?"
 
"He had a little laboratory in our garden at Sellithwaite," she continued. "He spent all his spare time in it—he'd done that for years. Lately, I know, he'd been trying to invent or discover something—I don't know what. But just before we left Sellithwaite, he told me that he'd solved the problem, and when he was sorting out and packing up his papers he showed me a sealed envelope in which he said were the particulars of his big discovery—he said there was a potential fortune in it and that he should die a rich man. I saw him put that envelope in a pocket-book which he always carried with him."
 
"That would be the pocket-book I examined last night," said Matherfield. "There was no sealed envelope, nor one of which any seal had been broken, in that. There was nothing but letters, receipts and unimportant papers."
 
"It is not in his other pocket-books," declared Rhona. "I went through all his things myself very early this morning—through everything that he had here. I know that he had that envelope yesterday—he pulled out some things from his pocket when we were lunching with Mr. Kenthwaite in a restaurant in Fleet Street, and I saw the envelope. It was a stout, square envelope, across the front of which he had drawn two thick red lines, and it was heavily sealed with black sealing-wax at the back."
 
"That was yesterday, you say?" asked Matherfield sharply. "Yesterday noon? Just so! Then as he had it yesterday at noon, and as it wasn't in his pockets last night and is not among his effects in this house, it's very clear that between, say, two o'clock yesterday and midnight he parted with it. Now then, to whom? That's a thing we've just got to find out! But you're sure he wasn't joking when he told you that this discovery, or invention, or whatever it was, was worth a potential fortune?"
 
"On the contrary, he was very serious," replied Rhona. "Unusually serious for him. He wouldn't tell me what it was, nor give me any particulars—all he said was that he'd solved a problem and hit on a discovery that he'd worked over for years, and that the secret was in that envelope and worth no end of money. I asked him what he meant by no end of money and he said: 'Well, at any rate, a hundred thousand pounds—in time.'"
 
The two men exchanged glances; silence fell on the whole group.
 
"Oh!" said Matherfield at last. "A secret worth a hundred thousand pounds—in time. This will have to be looked into—narrowly. What do you think, Mr. Hetherwick?"
 
"Yes," answered Hetherwick. "You've no idea, of course, as to whether your grandfather had done anything about putting this discovery on the market—or made any arrangement about selling it? No! Well, can you tell me this: What sort of house did your grandfather want to rent here in London? I mean, do you know what rent he was prepared to pay?"
 
"I can answer that," remarked Mrs. Keeley. "He told me he wanted a good house—a real good one—in a convenient suburb, and he was willing to go up to three hundred a year."
 
"Three hundred a year," said Hetherwick. He exchanged a meaning glance with Matherfield. "That," he added, "looks as if he felt assured of a considerable income, and as though he had already realised on his discovery or was very certain of doing so."
 
"To be sure," agreed Matherfield. "Of course, I don't know what his private means were, but I know what his retiring pension would be—and three hundred a year for rent alone means—a good deal! Um!—we'll have to endeavour to trace that sealed envelope."
 
"It seems to me, Matherfield," observed Hetherwick, "that the first thing to do is to trace Hannaford's movements last night, from the time he left this hotel until his death in the train."
 
"We're at that already," replied Matherfield. "We've a small army of men at work. But as we want all the help we can get, I'm going to stir up the newspaper men, Mr. Hetherwick—the Press, sir, is always valuable in this sort of thing!—and I want Miss Hannaford, if she's got one, to give me a recent photograph of her grandfather so that it can appear in the papers. Somebody, you know, may recognise it—somebody who saw him last night with somebody else."
 
Rhona had a new photograph of the dead man, taken in plain clothes just before he left Sellithwaite, and she gave Matherfield some copies of it. Reproductions appeared in the Meteor and other evening papers that night, and in some of the dailies next morning. And, as a result, a man came forward at the inquest, a few hours later, who declared with positive assurance that he had seen Hannaford early in the evening of the murder. His appearance was the only sensational thing about these necessarily only preliminary proceedings before the coroner; until he stepped forward nothing had transpired with which Hetherwick was not already familiar. There had been his own evidence; somewhat to his surprise neither coroner nor police seemed to pay much attention to his account of the conversation about the woman's portrait; they appeared to regard Hannaford's observations as a bit of garrulous reminiscence about some criminal or other. There had been Rhona's—a repetition of what she had told Matherfield and Hetherwick at Matter's Hotel: police and coroner evidently fixed on the missing sealed envelope and its mysterious secret as a highly important factor in the case. Then there had been the expert testimony of the two doctors as to the cause of death—that had been confined to positive declarations that Hannaford died from the administration of some subtle poison, the exact details being left over until experts could tell more at the adjourned proceedings. And the coroner was about to adjourn for a fortnight when a man, who had entered the court and been in conversation with the officials, was put into the witness-box to tell a story which certainly added information and, at the same time, accentuated mystery.
 
This man was a highly-respectable person in appearance, middle-aged, giving the name of Martin Charles Ledbitter, manager of an insurance office in Westminster, and residing at Sutton, in Surrey. It was his habit, he said, to travel every evening from Victoria to Sutton by the 7.20 train. As a rule he arrived at Victoria just before seven and took a cup of tea in the refreshment-room. He did this on the night before last. While he was drinking his tea at the counter, an elderly man came in and stood by him, whom he was sure beyond doubt was the same man whose photograph was reproduced in some of last night's and some of this morning's newspapers. He had no doubt whatever about this. He first noticed the man's stained fingers as he took up the glass of whisky-and-soda which he had ordered; he had, at the time, wondered at the contrast between those fingers and the general spick-and-spanness of the man and his smart attire; also he had noticed his gold-headed walking-cane and that the head was fashioned like a crown. They stood side by side for some minutes, then the man went out. A minute or two later he saw him again—this time at the right-hand side bookstall; he was there obviously looking out for somebody.
 
This was the point where the interest really began; everybody in court strained eyes and ears as the coroner put a direct question.
 
"Looking out for somebody? Did you see him meet anybody?"
 
"I did!"
 
"Tell me what you saw."
 
"I saw this. When I approached the bookstall, to buy some evening papers, the man whom I had seen in the refreshment-room was standing close by. He was looking about him, but chiefly at the entrances to the big space between the offices and the platforms. Once or twice he looked at his watch. It was then—by the station clock—about ten minutes past seven. He seemed impatient; he moved restlessly about. I passed him and went to the bookstall. When I turned round again he was standing a few yards away, shaking hands with another man. From the way in which they shook hands, I concluded that they were old friends, who perhaps had not seen each other for some time."
 
"Their greeting was cordial?"
 
"I should call it effusive."
 
"Can you describe the other man?"
 
"I can describe a sort of general impression of both. He was a tall man, taller than Hannaford, but not so broadly built. He wore a dark ulster overcoat, with a strap at the back; it was either a very dark blue or a black in colour. He had a silk hat—new and glossy. He gave me the impression of being a smartly-dressed man—smart boots and gloves and that sort of thing—you know the general impression you get at a quick glance. But as to his features, I can't tell you anything."
 
"Why not?" asked the coroner.
 
"Because, to begin with, he wore an unusually large pair of blue spectacles, which completely veiled his eyes, and to end with, his throat and chin were swathed in a heavy white muffler, which covered the lower part of his face as well. Between the rim of his hat and the collar of his coat it was all muffler and spectacles!"
 
The coroner looked disappointed. His interest in the witness seemed to evaporate.
 
"Did you notice anything else?" he asked.
 
"Only that the new-comer took Hannaford's arm and that they walked away towards the left-hand entrance hall, evidently in earnest conversation. That was the last I saw of them."
 
"There's just one question I should like to put to you in conclusion," said the coroner. "You say that you are confident that the photograph in the newspapers is that of the man you saw at Victoria. Now, have you seen the dead man's body?"
 
"I have. The police took me to see it when I volunteered my evidence."
 
"And you recognised it as that of the man you saw?"
 
"Without doubt! There is no question of that in my mind."
 
Five minutes later the inquest stood adjourned, and those chiefly concerned gathered together in the emptying court to discuss the voluntary witness's evidence. Matherfield manifested an almost cheerful optimism.
 
"This is better!—much better," he declared, rubbing his hands as if in anticipation of laying them on something. "We know now that Hannaford met, at any rate, two men that night. It's easier to find two men than one!"
 
Rhona, whom Hetherwick had escorted to the coroner's court, looked her astonishment. "How can that be?" she asked.
 
"Mr. Hetherwick understands," answered Matherfield with a laugh. "He'll tell you."
 
But Hetherwick said nothing. He was always wondering—always wondering—about the woman whose picture lay in his pocket.