Stoner knew how that half-sheet of foolscap had come into his possession. It was a half-sheet which he had found on Cotherstone's desk when he went into the partners' private room to tidy things up on the morning after the murder of Kitely. It lay there, carelessly tossed aside amongst other papers of clearer meaning, and Stoner, after one glance at it, had carefully folded it, placed it in his pocket, taken it home, and locked it up, to be inspected at leisure.
He had had his reasons, of course, for this abstraction of a paper which rightfully belonged to Cotherstone. Those reasons were a little difficult to explain to himself in one way; easy enough to explain, in another. As regards the difficulty, Stoner had somehow or other got a vague idea, that evening of the murder, that something was wrong with Cotherstone. He had noticed, or thought he noticed, a queer look on old Kitely's face when the ex-detective left the private room—it was a look of quiet satisfaction, or triumph, or malice; any way, said Stoner, it was something. Then there was the fact of Cotherstone's curious abstraction when he, Stoner, entered and found his employer sitting in the darkness, long after Kitely had gone—Cotherstone had said he was asleep, but Stoner knew that to be a fib. Altogether, Stoner had gained a vague feeling, a curious intuition, that there was something queer, not unconnected with the visit of Cotherstone's new tenant, and when he heard, next morning, of what had befallen Kitely, all his suspicions were renewed.
So much for the difficult reasons which had made him appropriate the half-sheet of foolscap. But there was a reason which was not difficult. It lay in the presence of that word Wilchester. If not of the finest degree of intellect, Stoner was far from being a fool, and it had not taken him very long to explain to himself why Cotherstone had scribbled the name of that far-off south-country town all over that sheet of paper, aimlessly, apparently without reason, amidst his figurings. It was uppermost in his thoughts at the time—and as he sat there, pen in hand, he had written it down, half-unconsciously, over and over again.... There it was—Wilchester—Wilchester—Wilchester.
The reiteration had a peculiar interest for Stoner. He had never heard Cotherstone nor Mallalieu mention Wilchester at any time since his first coming into their office. The firm had no dealings with any firm at Wilchester. Stoner, who dealt with all the Mallalieu & Cotherstone correspondence, knew that during his five and a half years' clerkship, he had never addressed a single letter to any one at Wilchester, never received a single letter bearing the Wilchester post-mark. Wilchester was four hundred miles away, far off in the south; ninety-nine out of every hundred persons in Highmarket had never heard the name of Wilchester. But Stoner had—quite apart from the history books, and the geography books, and map of England. Stoner himself was a Darlington man. He had a close friend, a bosom friend, at Darlington, named Myler—David Myler. Now David Myler was a commercial traveller—a smart fellow of Stoner's age. He was in the service of a Darlington firm of agricultural implement makers, and his particular round lay in the market-towns of the south and south-west of England. He spent a considerable part of the year in those districts, and Wilchester was one of his principal headquarters: Stoner had many a dozen letters of Myler's, which Myler had written to him from Wilchester. And only a year before all this, Myler had brought home a bride in the person of a Wilchester girl, the daughter of a Wilchester tradesman.
So the name of Wilchester was familiar enough to Stoner. And now he wanted to know what—what—what made it so familiar to Cotherstone that Cotherstone absent-mindedly scribbled it all over a half-sheet of foolscap paper?
But the figures? Had they any connexion with the word? This was the question which Stoner put to himself when he sat down that night in his parlour to seriously consider if he had any chance of winning that five hundred pounds reward. He looked at the figures again—more carefully. The truth was that until that evening he had never given much attention to those figures: it was the word Wilchester that had fascinated him. But now, summoning all his by no means small arithmetical knowledge to his aid, Stoner concentrated himself on an effort to discover what those figures meant. That they were a calculation of some sort he had always known—now he wanted to know of what.
The solution of the problem came to him all of a sudden—as the solution of arithmetical problems often does come. He saw the whole thing quite plainly and wondered that he had not seen it at a first glance. The figures represented nothing whatever but three plain and common sums—in compound arithmetic. Cotherstone, for some reason of his own, had taken the sum of two thousand pounds as a foundation, and had calculated (1st) what thirty years' interest on that sum at three and a half per cent. would come to; and (2nd) what thirty years' interest at five per cent. would come to; and (3rd) what the compound interest on two thousand pounds would come to—capital and compound interest—in the same period. The last reckoning—the compound interest one—had been crossed over and out with vigorous dashes of the pen, as if the calculator had been appalled on discovering what an original sum of two thousand pounds, left at compound interest for thirty years, would be transformed into in that time.
All this was so much Greek to Stoner. But he knew there was something in it—something behind those figures. They might refer to some Corporation financial business—Cotherstone being Borough Treasurer. But—they might not. And why were they mixed up with Wilchester?
For once in a way, Stoner took no walk abroad that night. Usually, even when he stopped in of an evening, he had a brief stroll to the Grey Mare and back last thing before going to bed. But on this occasion he forgot all about the Grey Mare, and Popsie the barmaid did not come into his mind for even a second. He sat at home, his feet on the fender, his eyes fixed on the dying coals in the grate. He thought—thought so hard that he forgot that his pipe had gone out. The fire had gone out, too, when he finally rose and retired. And he went on thinking for a long time after his head had sought his pillow.
"Well, it's Saturday tomorrow, anyway!" he mused at last. "Which is lucky."