“You haven’t heard—­no one outside has heard—­of the strange illness and the robbery of my employer, Mr. Mansfield—­’Diamond Jack’ Mansfield, you know.”

Our visitor was a slight, very pretty, but extremely nervous girl, who had given us a card bearing the name Miss Helen Grey.

“Illness—­robbery?” repeated Kennedy, at once interested and turning a quick glance at me.

I shrugged my shoulders in the negative.  Neither the Star nor any of the other papers had had a word about it.

“Why, what’s the trouble?” he continued to Miss Grey.

“You see,” she explained, hurrying on, “I’m Mr. Mansfield’s private secretary, and—­oh, Professor Kennedy, I don’t know, but I’m afraid it is a case for a detective rather than a doctor.”  She paused a moment and leaned forward nearer to us.  “I think he has been poisoned!”

The words themselves were startling enough without the evident perturbation of the girl.  Whatever one might think, there was no doubt that she firmly believed what she professed to fear.  More than that, I fancied I detected a deeper feeling in her tone than merely loyalty to her employer.

“Diamond Jack” Mansfield was known in Wall Street as a successful promoter, on the White Way as an assiduous first-nighter, in the sporting fraternity as a keen plunger.  But of all his hobbies, none had gained him more notoriety than his veritable passion for collecting diamonds.

He came by his sobriquet honestly.  I remembered once having seen him, and he was, in fact, a walking De Beers mine.  For his personal adornment, more than a million dollars’ worth of gems did relay duty.  He had scores of sets, every one of them fit for a king of diamonds.  It was a curious hobby for a great, strong man, yet he was not alone in his love of and sheer affection for things beautiful.  Not love of display or desire to attract notice to himself had prompted him to collect diamonds, but the mere pleasure of owning them, of associating with them.  It was a hobby.

It was not strange, therefore, to suspect that Mansfield might, after all, have been the victim of some kind of attack.  He went about with perfect freedom, in spite of the knowledge that crooks must have possessed about his hoard.

“What makes you think he has been poisoned?” asked Kennedy, betraying no show of doubt that Miss Grey might be right.

“Oh, it’s so strange, so sudden!” she murmured.

“But how do you think it could have happened?” he persisted.

“It must have been at the little supper-party he gave at his apartment last night,” she answered, thoughtfully, then added, more slowly, “and yet, it was not until this morning, eight or ten hours after the party, that he became ill.”  She shuddered.  “Paroxysms of nausea, followed by stupor and such terrible prostration.  His valet discovered him and sent for Doctor Murray—­ and then for me.”

“How about the robbery?” prompted Kennedy, as it became evident that it was Mansfield’s physical condition more than anything else that was on Miss Grey’s mind.