For some moments Thorndyke stood by the bench looking down on this powdering of grey that occupied the middle of the sheet of white paper. Some of the particles, such as vegetable fibres, were easily recognizable by the unaided eye; and there were two hairs, evidently moustache hairs, both quite short and of a tawny brown colour. But he made no detailed examination of the deposit. Taking from the cupboard a largish flat pill-box, he wrote on its lid the number of the box, and then, having lightly folded the sheet of paper, carefully assembled the dust into a tiny heap in the middle and transferred it to the pill-box, applying the tuning-fork to the sheet to propel the last few grains to their destination. Then, having put the box aside and deposited the sheets of tissue paper—neatly folded—in a numbered envelope, he spread a fresh sheet of demy on the bench, and taking up another box from the side-table, subjected it to similar treatment; and so, carefully and methodically, he dealt with the entire collection of boxes, never pausing for more than a rapid glance at the sprinkling of dust that each one yielded.
He was just shooting the ‘catch’ from the last package into the pill-box when a quick step was audible on the stairs, and after a short interval Polton let himself in silently.
“Here’s Dr. Jervis, sir,” said he, “and he says he hasn’t had lunch yet. It is past three o’clock, sir.”
“A very delicate hint, Polton,” said Thorndyke. “I will join him immediately—but here he is, guided by instinct at the very psychological moment.”
As he spoke, Dr. Jervis entered the room and looked about him inquisitively. From the row of pill-boxes his glance travelled to the little heaps of jewellery, each on a numbered sheet of paper.
“This is a quaint collection, Thorndyke,” said he, stooping to inspect the jewels. “What is the meaning of it? I trust that my learned senior has not, at last, succumbed to temptation; but it is a suspicious looking lot.”
“It does look a little like a fence’s stock-in-trade or the product of a super-burglary,” Thorndyke admitted. “However, I think Polton will be able to reassure you, when he has looked over the swag. But let us go and feed; and I will give you an outline sketch of the case in the intervals of mastication. It is quite a curious problem.”
“And I take it,” said Jervis, “that those pill-boxes contain the solution. There is a necromantic look about them that I seem to recognize. You must tell me about them when you have propounded the problem.”
He followed Thorndyke into the little breakfast-room, and when they had taken their seats at the table and fairly embarked on their immediate business, the story of the gem robbery was allowed to transpire gradually. Jervis followed the narrative with close attention and an occasional chuckle of amusement.
“It is an odd problem,” he commented when the whole story had been told. “There doesn’t seem to be any doubt as to who committed the robbery; and yet if you were to put this man Osmond into the dock, although the jury would be convinced to a man of his guilt, they would have to acquit him. I wonder what the deuce made him bolt.”
“Yes,” said Thorndyke, “that is what I have been asking myself. He may be a nervous, panicky man, but that does not look like the explanation. The suggestion is rather that he knew of some highly incriminating fact which he expected to come to light, but which has not come to light. As it is, the only incriminating fact is his own disappearance, which is evidentially worthless by itself.”
“Perfectly. And you are now searching for corroborative facts in the dust from those boxes. It doesn’t look a very hopeful quest.”
“It doesn’t,” Thorndyke agreed. “But still, circumstantial evidence gains weight very rapidly. A grain of positive evidence would give quite a new importance to the disappearance. For instance, no less than seven of those boxes have yielded moustache hairs, all apparently from the same person—a fair man with a rather closely cropped moustache of a tawny colour. Now, if it should turn out that Osmond has a moustache of that kind and that no other person connected with those boxes has a moustache of precisely that character, this would be a really important item of evidence, especially coupled with the disappearance.”
“It would, indeed; and even the number might be illuminating. I mean that, although moustache hairs are shed pretty freely, one would not have expected to find so many. But if the man had the not uncommon habit of stroking or rubbing his moustache, that would account for the number that had got detached.”
Thorndyke nodded approvingly. “Quite a good point, Jervis. I will make a note of it for verification. And now, as we seem to have finished, shall we take a look at one or two of the samples.”
“Exactly what I was going to propose,” replied Jervis; and as they rose and repaired to the small laboratory, he added: “It’s quite like old times to be pursuing a mysterious unknown quantity with you. I sometimes feel like chucking the insurance job and coming back.”
“It is better to come back occasionally and keep the insurance job,” Thorndyke rejoined as he placed two microscopes on the bench facing the window and drew up a couple of chairs. “You had better note the number of each box that you examine, though it is probably of no consequence.”
He took up the collection of pill-boxes, and having placed them between the two microscopes, sat down, and the two friends then fell to work, each carefully tipping the contents of a box on to a large glass slip and laying the latter on the stage of the microscope.
For some time they worked on in silence, each jotting down on a note-block brief comments on the specimens examined. When about half of the boxes had been dealt with—and their contents very carefully returned to them—Jervis leaned back in his chair and looked thoughtfully at his colleague.
“This is very commonplace, uncharacteristic dust in most respects,” said he, “but there is one queer feature in it that I don’t quite make out. I have found in every specimen a number of irregularly oval bodies, some of them with pointed ends. They are about a hundredth of an inch long by a little more than a two hundredth wide; a dull pink in colour and apparently of a granular homogeneous substance. I took them at first for insect eggs, but they are evidently not, as they have no skin or shell. I don’t remember having seen anything exactly like them before. Have you found any of them?”
“Yes. Like you, I have found some in every box.”
“And what do you make of them? Do you recognize them?”
“Yes,” replied Thorndyke. “They are the castings of a wood-boring beetle; particles of that fine dust that you see in the worm-holes of worm-eaten wood. Quite an interesting find.”
“Quite; unless they come from the boxes that the jewels were packed in.”
“I don’t think they do. Those boxes are white wood, whereas these castings are from a red wood. But we may as well make sure.”
He rose and took up the empty boxes one by one, turning each one over and examining it closely on all sides.
“You see, Jervis,” he said as he laid down the last of them, “there is not a trace of a worm-hole in any of them. No, that worm-dust came from an outside source.”
“But,” exclaimed Jervis, “it is very extraordinary. Don’t you think so? I mean,” he continued in response to an inquiring glance from his colleague, “that the quantity is so astonishing. Just think of it. In every one of these boxes we have found an appreciable number of these castings—quite a large quantity in the aggregate. But the amount of dust that will fall from a piece of worm-eaten furniture must be infinitesimal.”
“I would hardly agree to that, Jervis. A really badly wormed piece—say an old walnut chair or armoire—may, in the course of time, shed a surprisingly large amount of dust. But, nevertheless, my learned friend has, with his usual perspicacity, laid his finger on the point that is of real evidential importance—the remarkable quantity of this dust and its more or less even distribution among all these boxes. And now you realize the truth of what I was saying just now as to the cumulative quality of circumstantial