Bark quailed visibly before the eyes of his companion. He ceased to stand upright. His back was bowed and bent, his head was buried in his shoulders. His jaunty air vanished. The cynical smile faded from his lips. The pallor of his face and a shadow of fear in his eyes told their story.

"I swear I don't know what you mean," he said hoarsely. "For God's sake, don't talk like that, doctor. Oh, I am a bad lot, and I own it. Call me a scamp if you like, and I'll not deny it. You know all about me, doctor. But I am not as bad as all that. It had never occurred to me—no, not for all the money in the world—to do violence to a fellow-creature. I am innocent of bloodshed, if this is the last word that I am ever allowed to speak."

"Ah, now you are coming to your senses," Tanza said. "It is one thing to feel sure of a man's innocence, but it is another thing to prove it. Now, let us regard this matter from the point of view of the Crown Prosecutor who is opening the case against you. You have a sister who was Mrs. John Charlock's maid. This sister was carrying on an intrigue with a celebrated chemist whom we will call—but why make a parable of it? Let us call him by his proper name of Arnold Rent. This Rent was simply making a tool of your sister, because he wished to get her mistress's jewels. He is a far-seeing young man and, to use a common expression, has a pretty good notion of his own interest. Like many a clever young man before him, he has gone a bit too far. He is up to his eyes in debt and difficulty and dare not tell his mother, who is a bit of a fanatic in her way and quite capable of leaving her money elsewhere if she thinks her son is likely to make a bad use of it. Therefore he conceives the idea of getting hold of Mrs. Charlock's jewels. We won't go into the love affair, because that does not concern either of us, though it has a bearing on the story. Your sister Hortense acts as this man's tool and robs her mistress of her diamonds. For the present the stones are hidden in a secure place, which is known only to the thief and to Arnold Rent. It is just at this time that the thief discovers that she is merely a pawn in the game; it is her mistress who is the object of Rent's affections. The girl is beside herself with jealousy, though Rent manages to soothe her to a certain extent. For her own protection, however, she writes a letter to her brother, telling him how he can find the jewels in case anything happens to her. She is not too explicit as to the hiding-place, and this brother has to exercise his ingenuity as to the way in which the stones may be brought to light. At this point a tragedy occurs, and the girl is found dead in the fountain by the sundial in her employer's garden. Appearances point to suicide or accident. Nobody guesses that the poor woman is the victim of foul play, and I don't suppose they ever would if, perchance, I had not come here in my yacht for a little change and the thing happened to come to my ears. Rightly or wrongly, I concluded there was something wrong and sent for my friend Mr. Grey. To make a long story short, we discovered that I was absolutely right, and in a few hours we shall be able to prove that your sister was deliberately murdered. Whether Mrs. Charlock met with the same fate or not, we are not able at present to say. And now, Bark, are you going to deny your conviction, or stick to the fable that your sister's death was an accident? Didn't you come here with the intention of seeking out the hiding-place of those jewels? Take time to reply. You will gain nothing by lying. We happen to know where the jewels are, and we can put our hands upon them at any moment. We are not in the least afraid of being anticipated by you, because, even if we gave you a plan of the hiding-place, you couldn't touch them. If you attempted to do so, a third victim would be added to those who have already lost their lives in connexion with those ill-fated gems. You can please yourself whether you speak or not; if you like, I will unlock the door and send you ashore at once."

But Bark did not appear anxious to accept this offer. He sat writhing uneasily in his chair, his face turned eagerly to Tanza, as if waiting for the latter to continue. But the Italian said no more. He had given Bark his lesson and waited patiently for its effect.

"You are too many for me," Bark said presently. "You know too much. I might just as well tell the truth. My sister did write to me and tell me all about Arnold Rent, and I came here hot-foot to help her in the matter of those jewels. It was a shock to me to hear of her death, but I didn't suspect anything at the time. She was always a hot-headed, impulsive girl, and I naturally thought she had committed suicide. But when I came to inquire into the matter I formed another conclusion altogether. I asked myself a question or two, but I couldn't answer them. It occurred to me that perhaps Arnold Rent could. I had known him for some years. He is all right as men go, but put him in a tight place and he would stick at nothing. I thought the matter out, and at last I began to see my way. Hortense had been murdered. There was no doubt about that. But how had it been done? There were no marks of violence. There was nothing to show that she had met with a violent end, except that she was lying in the fountain. I couldn't get rid of the notion that Rent was in some way connected with this business, and I was confirmed in my opinion by his keeping out of my way. It is a pity he isn't able to tell us the truth. He knows all about it."

"You should have thought about that before you assaulted him," Grey put in quietly. "Don't forget that you are responsible for Rent's present mental condition."

A queer sort of laugh broke from Bark's lips.

"Oh, so you know about that, too?" he exclaimed. "It does not appear to be much good trying to keep anything from you gentlemen. Mind you, I didn't mean to do him any harm, but he refused to pay me money he owed me, and I lost my temper. If I had waited a bit longer I could have told him a thing or two which would have compelled him to listen to me. I could have forced him to give me all the money I needed. But there it is, and the thing can't be helped. And I don't think I could tell you any more if you kept me talking till daybreak. I'll help you all I can. I'll do anything you want me to do. I think I have sense enough to know when I am in a tight corner."

Tanza rose and unlocked the door.

"That is all at present. I should like to see the letter your sister wrote you—I mean the letter about the hidden jewels, which gave you the clue to the hiding-place. We can put you up for the night on the yacht, if you like; indeed, you will be well advised to stay here. I don't think, after what has happened, you are likely to play us false. You have had too severe a lesson."