But Sir Andrew rose reluctantly from his chair.

“I should like nothing better than to discuss this,” he said.  “But it is most important that I proceed to the House.  I should have been there some time ago.”  He turned toward the servant and directed him to call a hansom.

The gentleman with the pearl stud looked appealingly at the Naval Attache.  “There are surely many details that you have not told us,” he urged.  “Some you have forgotten.”

The Baronet interrupted quickly.

“I trust not,” he said, “for I could not possibly stop to hear them.”

“The story is finished,” declared the Naval Attache; “until Lord Arthur is arrested or the bodies are found there is nothing more to tell of either Chetney or the Princess Zichy.”

“Of Lord Chetney, perhaps not,” interrupted the sporting-looking gentleman with the black tie, “but there’ll always be something to tell of the Princess Zichy.  I know enough stories about her to fill a book.  She was a most remarkable woman.”  The speaker dropped the end of his cigar into his coffee-cup and, taking his case from his pocket, selected a fresh one.  As he did so he laughed and held up the case that the others might see it.  It was an ordinary cigar-case of well-worn pig-skin, with a silver clasp.

“The only time I ever met her,” he said, “she tried to rob me of this.”

The Baronet regarded him closely.

“She tried to rob you?” he repeated.

“Tried to rob me of this,” continued the gentleman in the black tie, “and of the Czarina’s diamonds.”  His tone was one of mingled admiration and injury.

“The Czarina’s diamonds!” exclaimed the Baronet.  He glanced quickly and suspiciously at the speaker, and then at the others about the table.  But their faces gave evidence of no other emotion than that of ordinary interest.

“Yes, the Czarina’s diamonds,” repeated the man with the black tie.  “It was a necklace of diamonds.  I was told to take them to the Russian Ambassador in Paris, who was to deliver them at Moscow.  I am a Queen’s Messenger,” he added.

“Oh, I see,” exclaimed Sir Andrew, in a tone of relief.  “And you say that this same Princess Zichy, one of the victims of this double murder, endeavored to rob you of—­of—­that cigar-case.”

“And the Czarina’s diamonds,” answered the Queen’s Messenger, imperturbably.  “It’s not much of a story, but it gives you an idea of the woman’s character.  The robbery took place between Paris and Marseilles.”

The Baronet interrupted him with an abrupt movement.  “No, no,” he cried, shaking his head in protest.  “Do not tempt me.  I really cannot listen.  I must be at the House in ten minutes.”

“I am sorry,” said the Queen’s Messenger.  He turned to those seated about him.  “I wonder if the other gentlemen—­” he inquired, tentatively.  There was a chorus of polite murmurs, and the Queen’s Messenger, bowing his head in acknowledgment, took a preparatory sip from his glass.  At the same moment the servant to whom the man with the black pearl had spoken, slipped a piece of paper into his hand.  He glanced at it, frowned, and threw it under the table.