Colwyn was upstairs in his bedroom preparing for his return journey to London when a meek knock and an apologetic cough reached his ears. He turned and saw Tufnell standing at the half-open door. The face of the old butler wore a look of mingled determination and nervousness—the expression of a timid man who had braced himself to a bold course of action after much irresolute deliberation.

"I beg your pardon, sir," he said, and his trepidation was apparent in his voice. "But might I—that is to say, could you spare me a few minutes' conversation?"

"Certainly," replied the detective. "Come inside, Tufnell. What is it?"

The butler entered the room and carefully closed the door behind him.

"I am sorry to interrupt you, sir," he said. "But I have just heard Miss Heredith give orders for your car to be got ready for your return to London, and I knew there was no time to be lost. It's about the—the murder, sir." He brought out the last words with an effort.

"Go on," said Colwyn, wondering what further surprise was in store for him.

"It's about something that happened on that night. I wanted to tell you before, but I didn't like to. After the murder was discovered I was sent over to the village to fetch the police and the doctor, and while I was hurrying through the woods near the moat-house I thought I saw a man crouching behind one of the trees near the carriage drive. He seemed to be looking towards me. When I looked again he was gone."

"And what did you do?"

"I called out, but received no answer, so I hurried on."

Colwyn scrutinized the butler with a thoughtful penetrating glance. The butler bore the look with the meek air of a domestic animal who knows that he is being appraised.

"Am I the first person to whom you have told this story?" the detective asked after a pause.

"Yes, sir."

"Why did you not inform the police officers when they were investigating the case?"

"For several reasons, sir. It seemed to me, when I came to think it over, that it must have been my fancy, and then it passed out of my mind in the worry and excitement of the house. Then, when I did think of it again, I didn't like to mention it to Superintendent Merrington, because he was such a bullying sort of gentleman that I felt quite nervous of him. Really, for a gentleman who has travelled with Royal Highnesses, as I've heard tell, and might be supposed to know how gentlemen behave, the way he treated the servants while he was here was almost too much for flesh and blood to bear." The butler's withered cheeks flushed faintly at the recollection. "I couldn't bring myself to tell him, sir."

Colwyn smiled slightly. He was not unacquainted with Merrington's methods of cross-examination.

"You could have spoken to Detective Caldew, the other officer engaged in the case," he said.

"Young Tom Caldew!" exclaimed the butler, in manifest surprise.

"You know him then?"

"I know him, but I cannot say I know any good of him," rejoined the butler severely. "Young Tom Caldew was born and bred in this village, and an idle young vagabond he was. Many a time have I dusted his jacket for stealing chestnuts in our park. The place was well rid of him, I take it, when he ran away to London and joined the police force. No, sir, I really couldn't see myself confiding in young Tom Caldew."

"And why have you confided in me now?"

"Well, sir, it was the arrest of the young woman that set me thinking, and caused me to wonder whether I'd done right in keeping this back. What I thought I saw that night may have been merely fancy on my part, but it took on an added importance in my mind when Miss Rath was arrested for murdering Mrs. Heredith. It seemed to me as though I might be doing some sort of injustice to her by not telling about it, and I wouldn't like to have that on my conscience after the way things turned out. But I thought it was too late to say anything after they had arrested Miss Rath and taken her away. Then Mr. Philip got better from his illness and went to London to fetch you. The same evening I heard Miss Heredith and Mr. Musard talking at the dinner table about the murder, and I gathered from what they said that Mr. Philip thought the detectives had made a mistake in arresting Miss Rath. Then I decided to tell you when you arrived, but I couldn't summon up my courage to do so until now," concluded the butler simply. "I hope I have done right, sir."

"You have certainly done right in not keeping the story to yourself any longer," said Colwyn. "Before I leave here you had better show me the place in the woods where you thought you saw this man."

"I shall be happy to do so, sir. I should like to thank you for listening to me. It is a weight off my mind."

"I shall be going almost immediately," continued Colwyn. "I think the best plan will be for you to meet me in the carriage drive, near the spot. Can you manage that?"

"Quite easily, sir."

"Excellent. And now, as you go downstairs, I should be glad if you would tell Mr. Musard that I should like to see him in my room before I go."

"Very well, sir. Afterwards you will find me waiting at the bend of the carriage drive where it winds round the lake."

Colwyn nodded his comprehension, and Tufnell left the room with a relieved countenance. A few moments later there was another knock at the door. In response to Colwyn's invitation the door opened, and Musard appeared.

"Tufnell said you wished to see me," he said, with an inquiring glance from beneath his dark brows.

"Yes. I should be glad if you would give me a description of the missing necklace. It will be useful in tracing it."

"It is not difficult to describe," replied Musard, seating himself on the edge of the bed. "It consisted of a single row of pink pearls, none of them very large. The biggest is about forty grains, and the others between twenty and thirty. It has a diamond clasp, set in antique gold, which is the most valuable part of the necklace. Do you know anything about jewels?"

"A little."

"Then you are aware that blue and red diamonds are the most valuable of stones. This diamond is a blue one—not very large, but a particularly fine stone."

"Of course the necklace is well-known to jewel experts?"

"As well-known as any piece of jewellery in Europe. Some of the pearls in it are hundreds of years old. It would be almost impossible for the thief to dispose of the necklace."

"It might be taken to pieces," suggested Colwyn.

"In order to hide its identity? Well, yes, but the selling value would be greatly reduced. The pearls have been strung."

"What about the diamond? Could not that be sold by the thief without risk of discovery?"

"Only by sending it to Amsterdam to get it cut into two or three smaller stones, so as to lessen the risk of detection. The Heredith blue diamond is known to many connoisseurs. It is cut in an unusual form—a kind of irregular rosette, in order to display its fire and optical properties to the best advantage. If it were cut it would lose a great deal of its value. The money value of one large diamond of first quality is very much greater than the same stone cut into three. But it would be difficult to sell the diamond in its present form. The chances are that it would be recognized in Hatton Garden—if it were offered for sale there."

"But if the diamond fell into the hands of somebody with a knowledge of precious stones he might keep it close for a while and then dispose of it abroad—in America, for instance," returned Colwyn. "That trick has been performed with better-known stones than the Heredith diamond. In fact, it strikes me as possible to sell the whole necklace that way. The disposal of the necklace depends largely upon who stole it—upon whether it has fallen into experienced or inexperienced hands. There are jewel dealers who ask no awkward questions if they can get things at their own price."

"Quite so," assented Musard, casting a quick glance at his companion's face. "It would be a risk, though—the thief might pick the wrong man. I can give you the addresses of two or three men in Hatton Garden who should be able to tell you if the necklace has been offered there. They know everything that is going on in the trade."

"I shall be glad to have them."

Musard scribbled several names and addresses on a leaf of his pocket-book, tore it out, and handed it to the detective.

"There is a curious coincidence about the loss of this, necklace," he remarked casually, as he rose to go. "It is another example of the misfortune which attaches to the possession of a blue diamond."

"Are you thinking of the Hope blue diamond? That certainly has a sinister history."

"That is the most notorious instance. But all blue diamonds are unlucky. I could tell you some gruesome stories connected with them. The previous wearer of the Heredith necklace—Philip's mother—died in giving birth to him. Incidentally, there is a curious legend attached to the moat-house in the form of a curse laid on it by the original builder, who was burnt alive in the old house. He prophesied that as the house of the Herediths was founded in horror it should end in horror. These old family curses sometimes come home to roost after a long lapse of time, though modern cynicism affects to sneer at such fancies. Of course, there may be nothing in it, but we have had more than enough horror in the moat-house recently, and poor Mrs. Heredith had a blue diamond in her room when she was murdered. But I must not keep you any longer, Mr. Colwyn. If there has been any miscarriage of justice in this terrible case I trust that you will be successful in bringing it to light."

He lingered after shaking hands, as though he would have liked to continue the conversation. Apparently not finding sufficient encouragement in the detective's face to do so, he turned and left the room, and Colwyn resumed his preparations for departure.

When they were completed he, too, went downstairs, carrying his bag. Miss Heredith and Phil were waiting to bid farewell to him. As Miss Heredith said good-bye, she looked into his face with the perplexed expression of a simple soul seeking reassurance from a stronger mind in the deep vortex of extraordinary events into which she had been plunged beyond her depth. Phil looked white and ill, and the hand which he gave into the detective's cool firm grasp was hot and feverish. While his aunt murmured those conventional phrases under which women seek to cover the realities of life as they bedeck corpses with flowers, Phil stood aside with the impatient air of one scornful of the futility of such things. As Miss Heredith ceased speaking he took a step forward, his dark eyes fixed eagerly and searchingly on Colwyn.

"You will lose no time?" he said. "You will find out everything?"

"I have already promised you that I will continue my investigations," replied Colwyn. The quiet sincerity of his words was the indication of a mind which despised the weakness of mere verbal emphasis.

"Lose no time. Spare no money," said Phil rapidly. His words and utterance contrasted forcibly with the stillness and composure of the man he was addressing. "Think what it means! Let me know everything that happens. Send me telegrams. Follow this thing out night and day. I depend on you—"

"Phil, Phil!" remonstrated Miss Heredith. "Mr. Colwyn has already promised to do all he can. You must be patient."

"Patience! My God, don't talk to me of patience," retorted her nephew fiercely. "I shall have no patience nor peace till this thing is settled."

Miss Heredith looked at him sadly. His breach of good manners in uttering an oath in her presence hurt her worse than a blow, but her heart sickened with the realization that it was but another manifestation of the complete change in him which had been brought about by his wife's murder. Colwyn brought the scene to a close.

"Of course I shall communicate with you," he said to Phil, as he took his departure. Phil accompanied him to his car, and stood under the portico watching him as he drove away. Colwyn glanced back as he crossed the moat-house bridge. The young man was still standing in the open doorway, looking after him. The next moment the bend of the carriage way hid him from view.

Colwyn encountered Tufnell at the next bend of the drive, waiting for him on the path under the trees which bordered the edge. The detective pulled up his car and stepped out.

"It was just off here, sir, that I thought I saw the figure that night," said the butler.

He plunged into a leafy avenue which led off the path at right angles, and followed it into the wood until he reached the mossy trunk of a great oak, which flung a gnarled arm horizontally across the narrow walk as though barring further intrusion into its domain. Tufnell stopped, and turned to the detective.

"It seemed to me as though a man was crouching just about here, sir," he said in a whisper, as if he feared that the intruder might still be hiding there and overhear his words.

Colwyn carefully examined the spot. The moss and grass where he stood grew fresh underfoot, with no marks to suggest that they had been trodden on recently. But close by, behind the horizontal branch of the great oak, was a tangled patch of undergrowth and brambles, broken and pressed down in places, as though it had been entered by a human being. As Colwyn was looking at this place, his eye was attracted by a yellow speck in the background of green. It was a tiny fragment of khaki, caught on one of the bramble bushes.