When Eugénie left the prison, she went straight to Naball's office, and finding him in, told all about the wonderful discovery of the veritable five-pound note endorsed in Isaiah's writing. To say that Naball was astonished would be a mild way to state his feelings on receipt of this intelligence.

"It's an uncommon piece of luck," he said, looking at the note; "we might have searched for a twelvemonth, and never come across this piece of evidence. I think we'll get to the bottom of things this time. You got it from Kitty Marchurst?"

"Yes, I got it yesterday in payment of my salary"

Naball whistled softly.

"Things look uncommon black against that young woman," he observed thoughtfully. "I didn't half believe that story of hers about Stewart's stealing the diamonds, and now this note turning up in her possession--humph!"

"But you don't think she's guilty?" said Eugénie, clasping her hands.

"I don't say anything," replied Naball savagely, for the difficulties of this case were beginning to irritate him. "I only say things look black against Caprice--she's as deep as a well."

"What are you going to do now?" asked Miss Rainsford in a trembling voice, as she rose to go.

The detective placed his hat jauntily on one side of his head, drew on his gloves, then taking his cane, walked to the door of the office, which he he held open for Eugénie to pass through.

"What are you going to do now?" she repeated when they were standing in the street.

"I'm going down to Toorak," said Naball quietly, "to trace this note, beginning with Kitty Marchurst as the last holder of it; she'll tell lies, but whether she does or not, I'll get to the bottom of this affair. Good-day, Miss Rainsford," and taking off his hat with a flourish, he left her abruptly, and strolled leisurely down the street.

Eugénie watched him with eager eyes until he was out of sight, and then turned round to walk home.

"Oh, my dear! my dear!" she murmured, "if I can only save you from this terrible danger--but not at the cost of that poor woman's life--oh, not that!"

The detective, on his way down to Toorak, went over the case in his own mind, in order to see against whom the evidence was strongest. At last, after considerable cogitation, he came to the conclusion that, after all, Villiers must be the guilty man, and that Kitty knew more about the crime than she chose to tell.

"I can't get over Villiers having had that diamond crescent," he thought, looking out of the carriage windows. "She denied it was hers, and then Fenton told me he gave it to her. I wonder if he had anything to do with the affair--humph!--not likely. If she thought it was him, she'd tell at once. Perhaps she really thinks Stewart stole the diamonds. Pish! I don't believe it. She's had a finger in the pie, whoever did it, and this murder is the outcome of the robbery. Well, I'll see if she can account for her possession of this five-pound note--that's the main thing."

Kitty Marchurst was at home, and sent a message to the detective that she would see him in a few minutes, so Naball walked up and down the long drawing-room with some impatience.

"If she'll only tell the truth," he muttered restlessly; "but I'm getting to doubt her, so that I can't be sure. There's one thing, Keith Stewart's fate rests entirely with her now, so if he saved her child's life, as she says he did, this is the time to prove her gratitude."

At this moment the door opened, and Caprice entered. She looked pale and weary, for the trials of the last few months had not been endured without leaving some mark of their passage. Naball did not know whether this haggard-looking woman was guilty or innocent, but he could not help pitying her, so worn-out did she seem.

"You are not well," he said when she seated herself.

Kitty sighed wearily, and pushed the loose hair off her forehead.

"No," she replied listlessly. "I'm getting worn-out over this trouble. It's no good my telling you anything, because you don't believe me. What is the matter now? Have you got further proof of my guilt?"

"I don't know," said Naball, coolly producing the five-pound note; "unless you call this proof."

"A five-pound note," she said contemptuously. "Well?"

"It is a five-pound note," explained Naball smoothly; "but not an ordinary one--in fact, it is one of the notes stolen from Lazarus's safe."

"Oh, how do you know that? By a very curious thing. One of the notes placed in the safe on the night of the murder was endorsed by the office-boy with the words 'Back Flat-Iron,' and strange to say the endorsed note has turned up."

"And that is it?"

"Exactly. Now, do you understand?"

Kitty shrugged her shoulders.

"I understand that you have secured an excellent piece of evidence, nothing more. Where did you get the note?"

"From Miss Rainsford."

"From Miss Rainsford!" repeated Kitty in surprise; "but you surely don't suspect--"

"No, I don't," interposed the detective; "because she was able to tell me where she got the note from."

"Well, I presume she got it from me."

"Yes," replied Naball, rather surprised at this cool admission. "She received it yesterday from you."

"Oh! then, you think I'm guilty?"

"Not if you can tell me where you got the note from."

"Certainly I can--from Mortimer--paid to me the day before yesterday."

"Your salary?"

"Not exactly," answered Kitty; "if it had been, you'd never be able to trace the note further back. No; I was at the theatre in the morning, and found myself short of money, so I asked Mortimer for some. He gave me that five-pound note, and, as he took it, from his waistcoat pocket, I've no doubt he'll be able to recollect from whom he received it."

"Why?"

"Because Mortimer doesn't carry fivers in his waistcoat pocket generally," said Caprice impatiently, "so he must have put that note there for some special reason. You'd better go and ask him."

"Certainly," said Naball, and arose to his feet. "I'm very much obliged to you."

"Then you don't think me guilty?" asked Kitty, with a smile.

"Upon my word, I don't know what to think," said the detective dismally. "The whole case seems mixed up. I'll tell you when I find the man who can't account for the possession of this fiver."

Kitty smiled, and then Naball took his leave, going straight from Toorak to the Bon-Bon Theatre, where he found Mortimer in his sanctum, up to the ears in business, as usual.

"Well, Naball," said the manager, looking up sharply, "what's up % Look sharp, I'm awfully busy."

"I only want to know where you got this?" asked Naball, giving him the five-pound note.

Mortimer took it up, and looked perplexed.

"How the deuce should I know; I get so many. Why do you want to know?"

"Oh, nothing. I just want to trace the note. Caprice said you gave it to her the day before yesterday."

"Eh! did I?"

"Yes. You took it from your waistcoat pocket."

"Of course; to be sure, she wanted some money. Yes; I kept it apart because it was made money--won it off Malton at euchre."

"Malton!" repeated Naball in amazement; "are you sure?"

"Yes, quite. You know I'm generally unlucky at cards, and this is about the first fiver I've made, so I kept it just to bring me luck; but Caprice wanted money, so I handed over my luck to her. There's nothing wrong, eh?"

"Oh, dear, no," replied Naball; "not the slightest--only some professional business."

"Because I shouldn't like to get any poor devil into a row," said Mortimer. "N............