It was in the August of 1889, when I was just arranging my annual holiday, that I received the following letter. I tore it open and read:—

"Theodora House-boat,    
Goring.

"Dear Mr. Bell,—

"Can you come down on Wednesday and stay with us for a week? The weather is glorious and the river looking its best. We are a gay party, and there will be plenty of fun going on.

"Yours very truly,    
"Helena Ridsdale."

This was exactly what I wanted. I was fond of the river, and scarcely a summer
passed that I did not spend at least a fortnight on the Thames. I could go for a week to the Ridsdales, and then start off on my own quiet holiday afterwards. I had known Lady Ridsdale since she was a girl, and I had no doubt my visit would prove a most enjoyable one. I replied immediately, accepting the invitation, and three days later arrived at Goring.

As the well-cushioned little punt, which had been sent to bring me across the river, drew up alongside the Theodora, the Countess came down from the deck to welcome me.

"I am so glad you could come, Mr. Bell," she said. "I was afraid you might be away on some of your extraordinary campaigns against the supernatural. This is Mr. Ralph Vyner; he is also, like yourself, devoted to science. I am sure you will find many interests in common."

A short, thickset, wiry little man, dressed in white flannels, who had been lolling in a deck chair, now came forward and shook hands with me.

"I know of you by reputation, Mr. Bell," he said, "and I have often hoped to have the pleasure of meeting you. I am sure we shall all be anxious to hear of some of your experiences. We are such an excessively frivolous party that we can easily afford to be leavened with a little serious element."

"But I don\'t mean to be serious in the least," I answered, laughing; "I have come here to enjoy myself, and intend to be as frivolous as the rest of you."

"You will have an opportunity this evening," said the Countess; "we are going to have a special band from town, and intend to have a moonlight dance on deck. Ah! here comes Charlie with the others," she added, shading her eyes and looking down the stream.

In a few moments a perfectly appointed little electric launch shot up, and my host with the rest of the party came on board. We shortly afterwards sat down to lunch, and a gayer and pleasanter set of people I have seldom met. In the afternoon we
broke up into detachments, and Vyner and I went for a long pull up stream. I found him a pleasant fellow, ready to talk at any length not only about his own hobbies, but about the world at large. I discovered presently that he was a naval engineer of no small attainments.

When we returned to the house-boat, it was nearly time to prepare for dinner. Most of the ladies had already retired to their cabins. Lady Ridsdale was standing alone on deck. When she saw us both, she called to us to come to her side.

"This quite dazzles me," she said in a low, somewhat mysterious tone, "and I must show it to you. I know you at least, Mr. Vyner, will appreciate it."

As she spoke she took a small leather case out of her pocket—it was ornamented with a monogram, and opened with a catch. She pressed the lid, it flew up, and I saw, resting on a velvet bed, a glittering circlet of enormous diamonds. The Countess lifted them out, and slipped them over her slender wrist.

"They are some of the family diamonds," she said with excitement, "and of great value. Charlie is having all the jewels reset for me, but the rest are not ready yet. He has just brought this down from town. Is it not superb? Did you ever see such beauties?"

The diamonds flashed on her white wrist; she looked up at me with eyes almost as bright.

"I love beautiful stones," she said, "and I feel as if these were alive. Oh, do look at the rays of colour in them, as many as in the rainbow."

I congratulated Lady Ridsdale on possessing such a splendid ornament, and then glanced at Vyner, expecting him to say something.

The expression on his face startled me, and I was destined to remember it by-and-by. The ruddy look had completely left it, his eyes were half starting from his head. He peered close, and suddenly, without the slightest warning, stretched out his hand, and touched the diamonds
as they glittered round Lady Ridsdale\'s wrist. She started back haughtily, then, recovering herself, took the bracelet off and put it into his hand.

"Charlie tells me," she said, "that this bracelet is worth from fifteen to twenty thousand pounds."

"You must take care of it," remarked Vyner; "don\'t let your maid see it, for instance."

"Oh, nonsense!" laughed Lady Ridsdale. "I would trust Louise as I would trust myself."

Soon afterwards we separated, and I went down to my little cabin to prepare for dinner. When we met in the dining saloon I noticed that Lady Ridsdale was wearing the diamond bracelet. Almost immediately after dinner the band came on board and the dancing began.

We kept up our festivities until two o\'clock, and more than once, as she flashed past me, I could not help noticing the glittering circlet round her wrist. I considered myself a fair judge of precious
stones, but had never seen any diamonds for size and brilliancy to equal these.

As Vyner and I happened to stand apart from the others he remarked upon them.

"It was imprudent of Ridsdale to bring those diamonds here," he said. "Suppose they are stolen?"

"Scarcely likely," I answered; "there are no thieves on board."

He gave an impatient movement.

"As far as we know there are not," he said slowly, "but one can never tell. The diamonds are of exceptional value, and it is not safe to expose ordinary folk to temptation. That small circlet means a fortune."

He sighed deeply, and when I spoke to him next did not answer me. Not long afterwards our gay party dispersed, and we retired to our respective cabins.

I went to mine and was quickly in bed. As a newly-arrived guest I was given a cabin on board, but several other members of the party were sleeping in tents on the
shore. Vyner and Lord Ridsdale were amongst the latter number. Whether it was the narrowness of my bunk or the heat of the night, I cannot tell, but sleep I could not. Suddenly through my open window I heard voices from the shore near by. I could identify the speakers by their tones—one was my host, Lord Ridsdale, the other Ralph Vyner. Whatever formed the subject of discourse it was evidently far from amicable. However much averse I might feel to the situation, I was compelled to be an unwilling eavesdropper, for the voices rose, and I caught the following words from Vyner:

"Can you lend me five thousand pounds till the winter?"

"No, Vyner, I have told you so before, and the reason too. It is your own fault, and you must take the consequences."

"Do you mean that to be final?" asked Vyner.

"Yes."

"Very well, then I shall look after myself. Thank God, I have got brains if I
have not money, and I shall not let the means interfere with the end."

"You can go to the devil for all I care," was the angry answer, "and, after what I know, I won\'t raise a finger to help you."

The speakers had evidently moved further off, for the last words I could not catch. But what little I heard by no means conduced to slumber. So Vyner, for all his jovial and easy manner, was in a fix for money, and Ridsdale knew something about him scarcely to his credit!

I kept thinking over this, and also recalling his words when he spoke of Lady Ridsdale\'s diamonds as representing a fortune. What did he mean by saying that he would not let the means interfere with the end? That brief sentence sounded very much like the outburst of a desperate man. I could not help heartily wishing that Lady Ridsdale\'s diamond circlet was back in London, and, just before I dropped to sleep, I made up my mind to speak to Ridsdale on the subject.

Towards morning I did doze off, but I
was awakened by hearing my name called, and, starting up, I saw Ridsdale standing by my side. His face looked queer and excited.

"Wake up, Bell," he cried; "a terrible thing has happened."

"What is it?" I asked.

"My wife\'s bracelet is stolen."

Like a flash I thought of Vyner, and then as quickly I knew that I must be careful to give no voice to hastily-formed suspicions.

"I won\'t be a moment dressing, and then I\'ll join you," I said.

Ridsdale nodded and left my cabin.

In five minutes I was with him on deck. He then told me briefly what had happened.

"Helena most imprudently left the case on her dressing-table last night," he said, "and owing to the heat she kept the window open. Some one must have waded into the water in the dark and stolen it. Perhaps one of the bandsmen may have noticed the flashing of the diamonds on
her wrist and returned to secure the bracelet—there\'s no saying. The only too palpable fact is that it is gone—it was valued at twenty thousand pounds!"

"Have you sent for the police?" I asked.

"Yes, and have also wired to Scotland Yard for one of their best detectives. Vyner took the telegram for me, and was to call at the police station on his way back. He is nearly as much upset as I am. This is a terrible loss. I feel fit to kill myself for my folly in bringing that valuable bracelet on board a house-boat."

"It was a little imprudent," I answered, "but you are sure to get it back."

"I hope so," he replied moodily.

Just then the punt with Vyner and a couple of policemen on board was seen rapidly approaching. Ridsdale went to meet them, and was soon in earnest conversation with the superintendent of police. The moment Vyner leapt on board he came to the part of the deck where I was standing.

"Ah, Bell," he cried, "what about my prognostications of last night?"

"They have been verified too soon," I answered. I gave him a quick glance. His eyes looked straight into mine.

"Have you any theory to account for the theft?" I asked.

"Yes, a very simple one. Owing to the heat of the evening the Countess slept with her window open. It was an easy matter to wade through the water, introduce a hand through the open window and purloin the diamonds."

"Without being seen by any occupants of the tents?" I queried.

"Certainly," he answered, speaking slowly and with thought.

"Then you believe the thief came from without?"

"I do."

"What about your warning to Lady Ridsdale yesterday evening not to trust her maid?"

I saw his eyes flash. It was the briefest of summer lightning that played in their
depths. I knew that he longed to adopt the suggestion that I had on purpose thrown out, but dared not. That one look was enough for me. I had guessed his secret.

Before he could reply to my last remark Lord Ridsdale came up.

"What is to be done?" he said; "the police superintendent insists on our all, without respect of persons, being searched."

"There is nothing in that," I said; "it is the usual thing. I will be the first to submit to the examination."

The police went through their work thoroughly, and, of course, came across neither clue nor diamonds. We presently sat down to breakfast, but I don\'t think we any of us had much appetite. Lady Ridsdale\'s eyes were red with crying, and I could see that the loss had shaken both her nerve and fortitude. It was more or less of a relief when the post came in. Amongst the letters I found a telegram for myself. I knew what it meant before I opened it. It was from a man in a distant part of the country whom I had promised
to assist in a matter of grave importance. I saw that it was necessary for me to return to town without delay. I was very loth to leave my host and hostess in their present dilemma, but there was no help for it, and soon after breakfast I took my leave. Ridsdale promised to write me if there was any news of the diamonds, and soon the circumstance passed more or less into the background of my brain, owing to the intense interest of the other matter which I had taken up. My work in the north was over, and I had returned to town, when I received a letter from Ridsdale.

"We are in a state of despair," he wrote; "we have had two detectives on board, and the police have moved heaven and earth to try and discover the bracelet—all in vain; not the slightest clue has been forthcoming. No one has worked harder for us than Vyner. He has a small place of his own further down the river, and comes up to see us almost daily. He has made all sorts of suggestions for the recovery of the diamonds,
but hitherto they have led to nothing. In short, our one hope now turns upon you, Bell; you have done as difficult things as this before. Will you come and see us, and give us the benefit of your advice? If any man can solve this mystery, you are the person."

I wrote immediately to say that I would return to the Theodora on the following evening, and for the remainder of that day tried to the best of my ability to think out this most difficult problem. I felt morally certain that I could put my hand on the thief, but I had no real clue to work upon—nothing beyond a nameless suspicion. Strange as it may seem, I was moved by sentiment. I had spent some pleasant hours in Vyner\'s society—I had enjoyed his conversation; I had liked the man for himself. He had abilities above the average, of that I was certain—if he were proved guilty, I did not want to be the one to bring his crime home to him. So uncomfortable were my feelings that at last I made up my mind to take a somewhat bold step. This was
neither more nor less than to go to see Vyner himself before visiting the house-boat. What I was to do and say when I got to him I was obliged to leave altogether to chance; but I had a feeling almost amounting to a certainty that by means of this visit I should ultimately return the bracelet to my friends the Ridsdales.

The next afternoon I found myself rowing slowly down the river, thinking what the issue of my visit to Vyner would be. It happened to be a perfect evening. The sun had just set. The long reach of river stretched away to the distant bend, where, through the gathering twilight, I could just see the white gates of the Eight-Mile Lock. Raising my voice, I sang out in a long-drawn, sonorous monotone the familiar cry of "Lock! lock! lock!" and, bending to the sculls, sent my little skiff flying down stream. The sturdy figure of old James Pegg, the lock-keeper, whom I had known for many years, instantly appeared on the bridge. One of the great gates slowly swung open, and, shipping my sculls, I shot
in, and called out a cheery good-evening to my old friend.

"Mr. Bell!" exclaimed the old fellow, hurrying along the edge of the lock. "Well, I never! I did not see it was you at first, and yet I ought to have known that long, swinging stroke of yours. You are the last person I expected to see. I was half afraid it might be some one else, although I don\'t know that I was expecting any one in particular. Excuse me, sir, but was it you called out \'Lock\' just now?"

"Of course it was," I answered, laughing. "I\'m in the deuce of a hurry to-night, Jimmy, as I want to get on to Wotton before dark. Look sharp, will you, and let me down."

"All right, sir—but you did frighten me just now. I wish you hadn\'t called out like that!"

As I glanced up at him, I was surprised to see that his usually ruddy, round face was as white as a sheet, and he was breathing quickly.

"Why, what on earth is the matter,
Jimmy?" I cried; "how can I have frightened you?"

"Oh, it\'s nothing, sir; I suppose I\'m an old fool," he faltered, smiling. "I don\'t know what\'s the matter with me, sir—I\'m all of a tremble. The fact is, something happened here last night, and I don\'t seem to have got over it. You know, I am all by myself here now, sir, and a lonely place it is."

"Something happened?" I said; "not an accident, I hope?"

"No, sir, no accident that I know of, and yet I have been half expecting one to occur all day, and I have been that weak I could hardly wind up the sluices. I am getting old now, and I\'m not the man I was; but I\'m right glad to see you, Mr. Bell, that I am."

He kept pausing as he spoke, and now and then glanced up the river, as if expecting to see a boat coming round the bend every moment. I was much puzzled by his extraordinary manner. I knew him to be a steady man, and one whose services were
much valued by the Conservancy; but it needed only a glance now to show that there was something very much amiss with him.

The darkness was increasing every moment, and, being anxious to get on as soon as possible, I was just going to tell him again to hurry up with the sluices, when he bent down close to me, and said,—

"Would you mind stepping out for a moment, sir, if you can spare the time? I wish to speak to you, sir. I\'d be most grateful if you would wait a minute or two."

"Certainly, Jimmy," I answered, hauling myself to the side with the boat-hook, and getting out. "Is there anything I can do for you? I am afraid you are not well. I never saw you like this before."

"No, sir; and I never felt like it before, that I can remember. Something happened here last night that has taken all the nerve out of me, and I want to tell you what it was. I know you are so clever, Mr. Bell, and I have heard about your doings up at Wallinghurst last autumn, when you cleared
up the Manor House ghost, and got old Monkford six months."

"Well, fire away," I said, filling my pipe, and wondering what was coming.

"It is this way, sir," he began. "Last night after I had had my supper I thought I\'d like a stroll and a quiet smoke along the towing path before turning in. I did not expect any more boats, as it was getting on for ten o\'clock. I walked about three-quarters of a mile, and was just going to turn round, when I saw a light down on the surface of the water in mid-stream. It was pretty dark, for the moon was not up yet, and there was a thick white mist rising from the water. I thought it must be some one in a canoe at first, so I waited a bit and watched. Then it suddenly disappeared, and the next instant I saw it again about a hundred yards or so higher up the stream, but only for a second, and then it went out. It fairly puzzled me to know what it could be, as I had never seen anything like it before. I felt sure it wasn\'t any sort of craft, but I had heard of strange lights being
seen at times on the water—what they call jack-o\'-lanterns, I believe, sir. I reckoned it might be one of them, but I thought I\'d get back to the lock, so that, if it was a canoe, I could let it through. However, nothing came of it, and I waited and watched, and worried all the evening about it, but couldn\'t come to any sort of idea, so I went to bed. Well, about one o\'clock this morning I suddenly woke up and thought I could hear some one a long way off calling exactly as you did just now, \'Lock! lock! lock!\' but it sounded ever so far away.

"\'It\'s some of those theatre people coming back to the Will-o\'-the-Wisp house-boat,\' I said to myself, \'and I\'m not going to turn out for them.\' The lock was full at the time, so I thought I would just let them work it for themselves. I waited a bit, expecting to hear them every minute come up, singing and swearing as they do, but they never came, and I was just dropping off when I heard the call again. It was not an ordinary sort of voice, but a
long, wailing cry, just as if some one was in trouble or drowning. \'Hi! hi! Lock! lo-oock!\' it went.

"I got up then and went out. The moon was up now and quite bright, and the mist had cleared off, so I went to the bridge on the upper gates and looked up stream. This is where I was standing, sir, just as we are standing now. I could see right up to the bend, and there was not the sign of a boat. I stood straining my eyes, expecting to see a boat come round every moment, when I heard the cry again, and this time it sounded not fifty yards up stream. I could not make it out at all, so I shouted out as loud as I could, \'Who are you? What\'s the matter?\' but there was no answer; and then suddenly, the next instant, close below me, from inside the lock this time, just here, ca............