She broke down again.  There was no doubt about the genuineness of her terror.  She seemed somehow to have shrunken into the semblance of a smaller woman.  The pupils of her eyes were distended, she was white almost to the lips.  When she recommenced her story, her voice was fainter.

“I saw a pair of hands—­just hands—­no arms—­nothing but hands—­come out of the darkness!  They gripped me by the throat.  I suppose it was just for a second.  I think—­I lost consciousness for a moment, although I was still standing up.  The next thing I remember is that I found myself shrieking and running here—­and the jewels had gone!”

“You saw no one?” her son asked incredulously.  “You heard nothing?”

“I heard no footsteps.  I saw no one,” Mrs. Rheinholdt repeated.

The Professor turned away.

“If you will allow me,” he begged, “I am going to telephone to my friend Mr. Sanford Quest, the criminologist.  An affair so unusual as this might attract him.  You will excuse me.”

The Professor hurried from the room.  They brought Mrs. Rheinholdt more champagne and she gradually struggled back to something like her normal self.  The dancing had stopped.  Every one was standing about in little groups, discussing the affair.  The men had trooped towards the conservatory, but the Professor met them on the portals.

[Illustration:  “Confess Thy sins, my good man.”]

[Illustration:  The black box is introduced into the story.]

“I suggest,” he said courteously, “that we leave the conservatory exactly as it is until the arrival of Mr. Sanford Quest.  It will doubtless aid him in his investigations if nothing is disturbed.  All the remaining doors are locked, so that no one can escape if by any chance they should be hiding.”

They all agreed without dissent, and there was a general movement towards the buffet to pass the time until the coming of Mr. Sanford Quest.  The Professor met the great criminologist and his assistant in the hall upon their arrival.  He took the former at once by the arm.

“Mr. Quest,” he began, “in a sense I must apologise for my peremptory message.  I am well aware that an ordinary jewel robbery does not interest you, but in this case the circumstances are extraordinary.  I ventured, therefore, to summon your aid.”

Sanford Quest nodded shortly.

“As a rule,” he said, “I do not care to take up one affair until I have a clean slate.  There’s your skeleton still bothering me, Professor.  However, where’s the lady who was robbed?”