there: a sort of pal of mine named Payne. He happened to be with me one evening when I called to collect my letters. Now, Payne chanced to be a good deal like me—at least he is tall and thin and stoops a bit; but he does not wear spectacles. He tried on my spectacles once for a joke, and then he really looked extremely like me. He looked in a mirror and remarked on the resemblance himself. Now, Payne did not belong to the Women’s League, and I suggest that he took advantage of this resemblance to get possession of this letter. He got a pair of spectacles like mine and personated me at the shop.”
“Why should he want to get possession of that letter?” Miller demanded.
“To plant it as he has planted it,” replied Pinder. “and set the police on a false trail.”
“This sounds pretty thin,” said Miller. “You are accusing this man of having murdered Mr. Burnham. What grounds have you for this accusation?”
“My grounds,” replied Pinder, “are, first, that he stole this letter which has been found, obviously planted; and, second, that he had a grudge against Burnham and knew all about his movements.”
“Indeed!” said Miller, with suddenly increased interest. “Then who and what is this man Payne?”
“Why,” replied Pinder, “until a month ago, he was assistant cashier at the Streatham branch of the bank. Then Burnham came down and hoofed him out without an hour’s notice. I don’t know what for, but I can guess.”
“Do you happen to know where Payne is at this moment?”
“Yes, I do. He is on this ship, in the smoking-room—only he is Mr. Shenstone now. And mighty sick he was when he found me on board.”
The superintendent looked at Thorndyke. “What do you think about it, doctor?” he asked.
“I think,” said Thorndyke,” that we had better have Mr. Shenstone in here and ask him a few questions. Would you see if you can get him to come here?” he added, addressing the purser, who had been listening with ecstatic enjoyment.
“I’ll get him to come along all right,” replied the purser, evidently scenting a new act in this enthralling drama; and away he bustled, all agog. In less than a minute we saw him returning down the alley-way, with a tall, thin man, who, at a distance, was certainly a good deal like Pinder, though the resemblance diminished as he approached. He, too, was obviously agitated, and seemed to be plying the purser with questions. But when he came opposite the door of the cabin he stopped dead and seemed disposed to shrink back.
“Is that the man?” Thorndyke demanded sharply and rather loudly, springing to his feet as he spoke.
The effect of the question was electrical. As Thorndyke rose, the newcomer turned, and, violently thrusting the purser aside, raced madly down the alley-way and out on to the deck.
“Stop that man!” roared Miller, darting out in pursuit; and at the shout a couple of loitering deck-hands headed the fugitive off from the gangway. Following, I saw the terrified man swerving this way and that across the littered deck to avoid the seamen, who joined in the pursuit; I saw him make a sudden frantic burst for a baggage-slide springing from a bollard up to the bulwark-rail. Then his foot must have tripped on a lashing, for he staggered for a moment, flung out his arms with a wild shriek, and plunged headlong into the space between the ship’s side and the quay wall.
In an instant the whole ship was in an uproar. An officer and two hands sprang to the rail with ropes and a boathook, while others manned the cargo derrick and lowered a rope with a running bowline between the ship and the quay.
“He’s gone under,” a hoarse voice proclaimed from below; “but I can see him jammed against the side.”
There were a couple of minutes of sickening suspense. Then the voice from below was heard again. “Heave up!”
The derrick-engine rattled, the taut rope came up slowly, and at length out of that horrid gulf arose a limp and dripping shape that, as it cleared the bulwark, was swung inboard and let down gently on the deck. Thorndyke and I stooped over him. But it was a dead man’s face that we looked into; and a tinge of blood on the lips told the rest of the tale.
“Cover him up,” said the superintendent. “He’s out of our jurisdiction now. But what’s going on there?”
Following his look, I perceived a small scattered crowd of men all running furiously along the quay towards the town. Some of them I judged to be the late inmates of the smoking-room and some plain-clothes men. The only figure that I recognised was that of Mr. Pinder, and he was already growing small in the distance.
“The local police will have to deal with them,” said Miller. Then turning to the purser, he asked: “What baggage had this man?”
“Only two cabin trunks,” was the reply. “They are both in his state-room.”
To the state-room we followed the purser, when Miller had possessed himself of the dead man’s keys, and the two trunks were hoisted on to the bunk and opened. Each trunk contained a large cash-box, and each cash-box contained five hundred pounds in gold and a big bundle of notes. The latter Miller examined closely, checking their numbers by a column of entries in his pocket-book.
“Yes,” he reported at length; “it’s a true bill. These are the notes that were stolen from Mr. Burnham. And now I will have a look at the baggage of those other four sportsmen.”
This being no affair of ours, Thorndyke and I went ashore and slowly made our way towards the town. But presently the superintendent overtook us in high glee, with the news that he had discovered what appeared to be the accumulated” swag “of a gang of swell burglars for whom he had been for some months vainly on the lookout.
“How was it done?” repeated Thorndyke in reply to Miller’s question, as we sat at a retired table in the “Lord Warden” Hotel. “Well, it was really very simple. I am afraid I shall disappoint you if you expect anything ingenious and recondite. Of course, it was obvious that Miss Dalby had not committed this atrocious murder and robbery; and it was profoundly improbable that this extremely incriminating letter had been dropped accidentally. That being so, it was almost certain that the letter had been ‘planted,’ as Pinder expressed it. But that was a mere opinion that helped us not at all. The actual solution turned upon a simple chemical fact with which I happened to be acquainted; which is this: that all the basic coal-tar dyes, and especially methylene blue, dye oxycellulose without requiring a mordant, but do not react in this way on cellulose. Now, good paper is practically pure cellulose; and if you dip a sheet of such paper into certain oxidising liquids, such as a solution of potassium chlorate with a slight excess of hydrochloric acid, the paper is converted into oxycellulose. But if instead of immersing the paper, you write on it with a quill or glass pen dipped in the solution, only the part which has been touched by the pen is changed into oxycellulose. No change is visible to the eye: but if a sheet of paper written on with this colourless fluid is dipped in a solution of, say, methylene blue, the invisible writing immediately becomes visible. The oxycellulose takes up the blue dye.
“Now, when I picked up that sheet of the letter in the railway carriage and noted that the ink used appeared to be methylene blue, this fact was recalled to my mind. Then, on looking at it closely, I seemed to detect a certain slight spottiness in the writing. There were points on some of the letters that were a little deeper in colour than the rest; and it occurred to me that it was possible that these circulars might be used to transmit secret messages of a less innocent kind than those that met the unaided eye, just as these political societies might form an excellent cover for
