Chettle laughed—a low, suggestive, satisfied chuckle. He laid the watch, its case still open, on the table at which they were standing, and tapped the photograph with the point of his finger.

"That may be the first step to the scaffold—for somebody," he said, with a meaning glance. "Ah—it's extraordinary what little, innocent-looking things help to put a bit of rope round a man's neck! So you took this, Mr. Allerdyke?—took it yourself, you say?"

"Took it myself, some eight or nine weeks ago," answered Allerdyke. "I took it in my garden one Sunday afternoon when my cousin James happened to be there. I do a bit in that way—amusement, you know. I just chanced to have a camera in my hand, and I saw James in a very favourable light and position, and I snapped him. And it was such a good 'un when developed that I printed off a few copies."

The detective's face became anxious.

"How many, now?" he asked. "How many, Mr. Allerdyke? I hope you can remember?—it's a point of the utmost seriousness."

"Naught easier," answered Allerdyke readily. "I've a good memory for little things as well as big 'uns. I printed off four copies. One of 'em I pasted into an album in which I keep particularly good photographs of my own taking; the other three I gave to him—he put 'em in his pocket-book."

"All unmounted—like this?" asked Chettle.

"All unmounted—like that," affirmed Allerdyke. "And now, then, since it seems to be a matter of importance, I can tell you what James did with at any rate two of 'em. He gave one to our cousin Grace—Mrs. Henry Mallins—a Bradford lady. He gave another to a friend of my own, another amateur photographer, Wilson Firth—gave him it in my presence at the Midland Hotel one day, when we were all three having a cigar together in the smoking-room there. Wilson Firth's a bit of a rival of mine in the amateur photographic line—we each try to beat the other, you understand. Now, then, James pulled one of these snapshots out and handed it over to Wilson with a laugh. 'There,' he says, 'that's our Marshall's latest performance—you'll have a job to do aught better than that, Wilson, my lad,' he says. So that accounts for two. And—this is the third!"

"And the question, Mr. Allerdyke, the big question—a most important question!—is, how did it come into this man Lydenberg's possession?" said the detective anxiously. "If we can find that out—"

"I've been thinking," interrupted Allerdyke. "There's this about it, you know: James and this Lydenberg came over together from Christiania to Hull in the Perisco. They talked to one another—that's certain. James may have given it to Lydenberg. But the thing is—is that likely?"

"No!" replied Chettle, with emphatic assurance. "No, sir! And I'll tell you why. If your cousin had given this photo to Lydenberg, as he might, of course, have given it to a mere passing acquaintance, because that acquaintance took a fancy to it, or something of that sort, Lydenberg would in all reasonable probability have just slipped in into his pocket-book, or put it loose amongst his letters and papers. But, as we see, however Lydenberg became possessed of this photo, he took unusual pains and precautions about it. You see, he cut it down, most carefully and neatly, to fit into the cover of his watch—he took the trouble to carry it where no one else would see it, but where he could see it himself at a second's notice—he'd nothing to do but to snap open that cover. No, sir, your cousin didn't give that photo to Lydenberg. That photo was sent to Lydenberg, Mr. Allerdyke—sent! And it was sent for one purpose only. What? That he should be able to identify Mr. James Allerdyke as soon as he set eyes on him!"

Allerdyke nodded his head—in complete understanding and affirmation. He was thinking the same thing—thinking, too, that here was at least a clue, a real tangible clue.

"Aye!" he said. "I agree with you. Then, of course, the one and only thing to do is—"

"To find out who the person was that your cousin gave this particular print to!" said Chettle eagerly. "Of course, it's a big field. So far as I understand things, he'd been knocking round a good bit between the time of your taking this photo and his death. He'd been in London, hadn't he? And in Russia—in two or three places. How can we find out when and how he parted with this? For give it to somebody he did, and that somebody was a person who knew of the jewel transaction, and employed Lydenberg in it, and sent the photo to Lydenberg so that he should know your cousin by sight—at once. Mr. Allerdyke, the secret of these murders and thefts is—there!"

Chettle replaced the watch in the cardboard box from which he had taken it, produced a bit of sealing-wax from his pocket, sealed up the box, and put it and the other things belonging to Lydenberg back in the small trunk from which he had withdrawn them to show his companion. And Allerdyke watched him in silence, wondering and speculating about this new development.

"What do you want me to do?" he asked suddenly. "You've got some scheme, of course, or you wouldn't have got me down here alone."

"Just so," agreed Chettle. "I have a scheme—and that's why I did get you down here alone. Mr. Allerdyke, you're a sharp, shrewd man—all you Yorkshiremen are!—at least, all that I've ever come across. You're good hands at ferreting things out. Now, Mr. Allerdyke, let's be plain—there's no two ways about it, no doubt whatever of it, the only people in England that we're aware of who knew about this Nastirsevitch jewel transaction are—Fullaway and whoever he has in his employ! We know of nobody else—unless, indeed, it's the Chicago millionaire, Delkin, and he's not very likely to have wanted to go in for a job of this sort. No, sir—Fullaway is the suspected person, in my opinion!—though I'm going to take precious good care to keep that opinion to myself yet awhile, I can tell you. Fullaway, Mr. Allerdyke, Fullaway!"

"Well?" demanded Allerdyke. "And so—"

"And so I want you to use your utmost ingenuity to find out if your cousin James gave that photo to Fullaway," continued Chettle. "We know very well that he was in touch with Fullaway before he went off to Russia—I have it in my notes that when Fullaway came to see you here in Hull, at the Station Hotel, the day of your cousin's death, he told you that he and Mr. James Allerdyke had been doing business for a couple of years, and that they'd last met in London about the end of March, just before your cousin set off on his journey to Russia. Is that correct?"

"Quite correct—to the letter," answered Allerdyke.

"Very well," said Chettle. "Now, according to you, that 'ud be not so very long after you took that snapshot of your cousin? So, he'd probably have the third print of it—the one we've just been looking at—on him when he was in London at that time?"

"Very likely," assented Allerdyke.

"Then," said Chettle with great eagerness, "try, Mr. Allerdyke, try your best and cleverest to find out if he gave it to Fullaway. You can think—you with a sharp brain!—of some cunning fashion of finding that out. What?"

"I don't know," replied Allerdyke, slowly and doubtfully. He possessed quite as much ingenuity as Chettle credited him with, but his own resourcefulness in that direction only inclined him to credit other men with the possession of just the same faculty. "I don't know about that. If James did give that print to Fullaway, and if Fullaway made use of it as you think, Fullaway'll be far too cute ever to let on that it was given to him. See!"

"I see that—been seeing it all through," answered Chettle. "All the same, there's ways and means. Think of something—you know Fullaway a bit by this time. Try it!"

"Oh, I'll try it, you bet!" exclaimed Allerdyke. "I'll try it for all it's worth, and as cleverly as I can. In fact, I've already thought of a plan, and if you don't want me any more just now, I'll go to the post-office and send off a telegram that's something to do with it."

"Nothing more now, sir," answered Chettle. "But look here—you're not going back to town to-night?"

"Why, that's just what I meant to do," replied Allerdyke. "There's naught to stop here for, is there?"

"I'm expecting a message from the Christiania police some time this afternoon or evening," said Chettle. "I cabled to them yesterday making full inquiries about Lydenberg—he represented himself here, to Dr. Orwin and the police-surgeons especially, as being a medical man in practice in Christiania, who had come across to Hull on some entirely private family business. Now, we've made the most exhaustive inquiries here in Hull—there isn't a soul in the town knows anything whatever of Lydenberg! I'm as certain as I am that I see you that he'd no business here at all—except to kill and rob your cousin. And so, of course, we want to know if he really was what he said he was, over there. I pressed upon the Christiania police to let me know all they could within thirty-six hours. So if you'll stop the night here, I'll likely be able to show you their reply to me."

"Right!" answered Allerdyke. "I'll put up at the Station Hotel. You come and have your dinner with me there at seven o'clock."

"Much obliged, Mr. Allerdyke," replied Chettle. "I'll come."

Then Allerdyke went off to the General Post Office and sent a telegram to his housekeeper in Bradford—

"Send off at once by registered parcel post to me at Waldorf Hotel, London, the morocco-bound photograph album lying on right-hand corner of my writing-desk in the library.—MARSHALL ALLERDYKE."

He went out of the post-office laughing cynically. Bit by bit things were coming out, he said to himself as he strolled away towards the hotel; link after link the chain was being forged. But around whom, in the end, was it going to be fastened? It was the first time in his life that he had ever been brought face to face with crime, and the seeking out of the criminal was beginning to fascinate him.

"Egad, it's a queer business!" he muttered. "A thread here, a thread there!—Heaven knows what it'll all come to. But this Chettle's a good 'un—he's like to do things."

Chettle joined him in the smoking-room of the hotel at a quarter to seven, and immediately produced a telegram.

"Came half an hour ago," he said as they sat down in a corner. "Nobody but myself seen it up to now. And—it's just what I expected. Read it."

Allerdyke slowly read the message through, pondering over it—

"We have made fullest inquiries concerning Lydenberg. He was certainly not in practice here either under that or any other name. Nothing is known of him as a resident in this city. We have definitely ascertained that he came to Christiania from Copenhagen, by land, via Lund and Copenhagen, arriving Christiania May 7th, and that he left here by steamship Perisco for Hull, May 10th."

"You notice the dates?" observed Chettle. "May 7th and 10th. Now, it was on May 8th that your cousin wired to Fullaway from Christiania, Mr. Allerdyke—there's no doubt about it! This man, Lydenberg, whoever he is or was, was sent to waylay your cousin at Christiania—sent from London. I've worked it out—he went overland—Belgium, Holland, Germany, Denmark, Sweden, Norway. Sounds a lot—but it's a quick journey. Sir—he was sent! And the sooner we find out about that photograph the better."

"I'm at work," answered Allerdyke. "Leave it to me."

He found his morocco-bound photograph album awaiting him when he arrived at the Waldorf Hotel next day, and during the afternoon he took it in his hand and strolled quietly and casually into Franklin Fullaway's rooms. Everything there looked as he had always seen it—Mrs. Marlow, charming as ever, was tapping steadily at her typewriter: Fullaway, himself a large cigar in his mouth, was reading the American newspapers, just arrived, in his own sanctum. He greeted Allerdyke with enthusiasm.

"Been away since yesterday, eh?" he said, after warm greetings. "Home?"

"Aye, I've been down to Yorkshire," responded Allerdyke offhandedly. "One or two things I wanted to see to, and some things I wanted to get. This is one of 'em."

"Family Bible?" inquired Fullaway, eyeing the solemnly bound album.

"No. Photos," answered Allerdyke. He was going to test things at once, and he opened the book at the fateful page. "I'm a bit of an amateur photographer," he went on, with a laugh. "Here's what's probably the last photo ever taken of James. What d'ye think of it?"

Fullaway glanced at the photograph, all unconscious that his caller was watching him as he had never been watched in his life. He waved his cigar at the open page.

"Oh!" he said airily. "A remarkably good likeness—wonderful! I said so when I saw it before—excellent likeness, Allerdyke, excellent! Couldn't be beaten by a professional. Excellent!"

Marshall Allerdyke felt his heart beating like a sledgehammer as he put his next question, and for the life of him he could not tell how he managed to keep his voice under control.

"Ah!" he said. "You've seen it before, then? James show it to you?"

Fullaway nodded towards the door of the outer room, from which came the faint click of the secretary's machine.

"He gave one to Mrs. Marlow the very last time he was here." he answered. "They were talking about amateur photography, and he pulled a print of that out of his pocket and made her a present of it; said it couldn't be beaten. You're a clever hand, Allerdyke—most lifelike portrait I ever saw. Well—any news?"