“Certainly!  With pleasure!” the Professor agreed, without glancing up.

His hostess sighed as she turned to leave the room.  She left the door ajar.  The Professor’s face was almost touching the glass case in which reposed the green beetle with yellow spots.

* * * * *

Mrs. Rheinholdt’s reception, notwithstanding the temporary absence of its presiding spirit, was without doubt an unqualified success.  In one of the distant rooms the younger people were dancing.  There were bridge tables, all of which were occupied, and for those who preferred the more old-fashioned pastime of conversation amongst luxurious surroundings, there was still ample space and opportunity.  Philip Rheinholdt, with a pretty young debutante upon his arm, came out from the dancing room and looked around amongst the little knots of people.

“I wonder where mother is,” he remarked.

“Looking after some guests somewhere, for certain,” the girl replied.  “Your mother is so wonderful at entertaining, Philip.”

“It’s the hobby of her life,” he declared.  “Never so happy as when she can get hold of somebody every one’s talking about, and show him off.  Can’t think what she’s done with herself now, though.  She told me—­”

The young man broke off in the middle of his sentence.  He, too, like many others in the room, felt a sudden thrill almost of horror at the sound which rang without warning upon their ears—­a woman’s cry, a cry of fear and horror, repeated again and again.  There was a little rush towards the curtained space which led into the conservatories.  Before even, however, the quickest could reach the spot, the curtains were thrown back and Mrs. Rheinholdt, her hands clasping her neck, her splendid composure a thing of the past, a panic-stricken, terrified woman, stumbled into the room.  She seemed on the point of collapse.  Somehow or other, they got her into an easy-chair.

“My jewels!” she cried.  “My diamonds!”

“What do you mean, mother?” Philip Rheinholdt asked quickly.  “Have you lost them?”

“Stolen!” Mrs. Rheinholdt shrieked.  “Stolen there in the conservatory!”

They gazed at her open-mouthed, incredulous.  Then a still, quiet voice from the outside of the little circle intervened.

“Instruct your servants, Mr. Rheinholdt, to lock and bar all the doors of the house,” the Professor suggested.  “No one must leave it until we have heard your mother’s story.”

The young man obeyed almost mechanically.  There was a general exodus of servants from the room.  Some one had brought Mrs. Rheinholdt a glass of champagne.  She sipped it and gradually recovered her voice.

“I had just taken the Professor into the little room my husband used to call the museum,” she explained, her voice still shaking with agitation.  “I left him there to examine some specimens of beetles.  I thought that I would come back through the conservatory, which is the quickest way.  I was about half-way across it when suddenly I heard the switch go behind me and all the electric lights were turned out.  I couldn’t imagine what had happened.  While I hesitated, I saw—­I saw—­”