Who had the opportunity? That depended, among other things, on the time at which the letter was posted. Penfield had stated that the letter had been posted at 8:30 p.m. If that were true, it put Varney out of the problem, for he had left Penzance some hours before that time. But it was not true. The time shown by the post-mark was not the time at which the letter was posted but that at which it was sorted at the post office. It might have been posted at a pillar-box some hours previously. It was therefore not impossible that it might have been posted by Varney. And if it was physically possible, it at once became the most probable assumption, since there was no reasonable alternative. It was inconceivable that Purcell should have handed the letters to a stranger to post, and if he had, it was inconceivable that that stranger should have opened the letters and transposed their contents. There was, indeed, the possibility that Purcell had met a confederate at Penzance and had handed him the letters—one of which would be addressed to himself—to post; and that this confederate might have made the transposition. But this was pure speculation without a particle of evidence to support it; whereas Varney, as an intimate friend, even if not a confederate, might conceivably have had the letters handed to him to post, though this was profoundly improbable, seeing that Purcell was going ashore and Varney was in charge of the yacht. In effect, there was no positive evidence that anybody had had the opportunity to make the transposition; but if it had not been done by Purcell, himself, then Varney appeared to be the only possible agent.
From this vague and unsatisfactory conclusion Thorndyke proceeded to the second question; assuming the transposition to have been made intentionally, what could have been the purpose of the act? To this question, so far as the immediate purpose was concerned, the answer was obvious enough, since only one was possible. The blanks must have been put into Mr. Penfield’s envelope for the express purpose of notifying the solicitor that Purcell was a bank-note forger; in short, for the purpose of exposing Purcell. This led at once to the third question: Who could have had such a purpose? But to this also the answer was obvious. The only person who could have had such a purpose would be a confederate; for no one else would have been in possession of the knowledge that would make such a purpose possible. The transposition could have been made only by some one who knew what the contents of the envelopes were.
But why should any confederate have done this? The exposure of Purcell involved at least a risk of the exposure of his confederate; and it could be assumed that if Purcell suspected that he had been betrayed, he would certainly denounce his betrayer. The object, therefore, could not have been to secure the arrest of Purcell, a conclusion that was confirmed by the fact that Purcell had become aware of the transposition, and if he had not done it himself, must apparently have been informed in time to allow of his escaping.
But what other object could there be? Was it possible that the confederate wished to get rid of Purcell and made this exposure with the express purpose of compelling him to disappear? That raised the question: When did Purcell become aware that the transposition had been made? And the answer was somewhat perplexing. He could not have become aware of it immediately, or he would have telegraphed to Penfield and stopped the letter; and yet he seemed to have absconded at once, before the letter could have been delivered to Penfield. He was due at Oulton the following day and he never arrived there. He was stated to have gone from Penzance to Falmouth. That might or might not be true; but the voyage to Ipswich was evidently a myth. The answer that he had received from the owners of the Hedwig, enclosing a report from the captain of the ship, showed that the only passengers who embarked at Falmouth were three distressed Swedish sailors, who travelled with the ship to Malmo, and that no one went ashore at Ipswich. It followed that Varney had either been misinformed or had invented the incidents; but when it was considered that he must, if he was telling the truth, have been misinformed in the same manner on two separate occasions, it seemed much more probable that the story of the voyage was a fabrication. In that case the journey to Falmouth—of which no one but Varney had heard—was probably a fabrication, too. This left Penzance as the apparent starting-point of the flight. Purcell had certainly landed at Penzance and had forthwith disappeared from view. What became of him thereafter it was impossible to guess. He seemed to have vanished into thin air.
Arrived at this point, Thorndyke’s quietly reflective attitude suddenly gave place to one of more intense attention. For a new and somewhat startling question had presented itself. With an expression of deep concentration, he set himself to consider it.
Hitherto he had accepted Purcell’s landing at Penzance as an undeniable fact from which a secure departure could be taken. But was it an undeniable fact? The only witness of that landing was Varney; and Varney had shown himself a very unreliable witness. Apparently he had lied about the Ipswich voyage; probably, too, about the visit to Falmouth. What if the landing at Penzance were a fabrication, too? It seemed a wild suggestion; but it was a possibility; and Thorndyke proceeded carefully to develop the consequences that would follow if it were true.
Suppose that Purcell had never landed at Penzance at all. Then several circumstances hitherto incomprehensible became understandable. The fables of Purcell’s appearance at Falmouth and Ipswich, which had seemed to be motiveless falsehoods, now showed a clear purpose; which was to create a certainty that Purcell had landed from the yacht as stated and to shift the search for the missing man from Penzance to Ipswich. Again, if Purcell had never landed at Penzance, the letter could not have been posted by him and it became practically certain that it must have been posted there by Varney and the transposition made by him. And this made the transposition understandable by developing a very evident purpose. When Penfield opened the letter and when, later, he heard of Purcell’s disappearance, he would at once assume that Purcell had absconded to avoid being arrested. The purpose of the transposition, then, was to furnish a reasonable explanation of a disappearance that had already occurred.
But what had become of Purcell? If he had not landed at Penzance, he certainly had not landed anywhere else, for there had not been time for the yacht to touch at any other port. Nor could it be supposed that he had transhipped on to another vessel during the voyage. There was no reason why he should. The letter had not been posted; and until it had been posted, there was no reason for flight. The only reasonable inference from the facts, including Varney’s false statements, was that something had happened during the voyage from Sennen; that Purcell had disappeared—presumably overboard—and that Varney had reasons for concealing the circumstances of his disappearance. In short, that Purcell was dead and that Varney was responsible for his death.
It was an appalling theory. Thorndyke hardly dared even to propound it to himself. But there was no denying that it fitted the facts with the most surprising completeness. Once assume it to be true and all the perplexing features of the case became consistent and understandable. Not only did it explain Varney’s otherwise inexplicable anxiety to prove that Purcell had been seen alive at a date subsequent to that of the alleged landing at Penzance; it accounted for the facts that Purcell had taken no measures to provide himself with a stock of cash before disappearing and that he had made no communication of any sort to his wife since his departure, though he could have done so with perfect safety. It was in perfect agreement with all the known facts and in disagreement with none. It was a complete solution of the mystery; and there was no other.
When Thorndyke reached this conclusion, he roused himself from his reverie, and, filling his pipe, took an impartial survey of the scheme of circumstantial evidence that he had been engaged in constructing. It was all very complete and consistent. There were, so far, no discrepancies or contradictions. All the evidence pointed in the one direction. The assumed actions of Varney were in complete agreement with the circumstances that were known and the others that were inferred as well as with the assumed motives. But it was largely hypothetical and might turn out to be entirely illusory. If only one of the assumed facts should prove to be untrue, the whole structure of inference would come tumbling down. He took out of his pocketbook the folded paper containing the single moustache hair that the Superintendent had found in the Clifford’s Inn rooms. Laying it on a sheet of white paper, he once more examined it, first through his lens, then under the microscope, noting the length, thickness and colour and mentally visualizing the kind of moustache from which it had come. Here was an indispensable link in the chain of evidence. If Purcell had had such a moustache, that would not prove that he and Bromeswell were one and the same person, but it would be consistent with their identity. But if Purcell had no such moustache, then it was probable—indeed, nearly certain—that he and Bromeswell were different persons. And if they were, the whole hypothetical scheme that he had been working out collapsed. Both Purcell and Varney ceased to have any connection with the forged notes; the mysterious “enclosures” could not be of the nature that he had assumed; and all the deductions from those assumed facts ceased to be valid. It was necessary without delay to test this essential link; to ascertain whether this derelict hair could have been derived from Daniel Purcell.