“Pud id down here, Laadham,” directed Mr. Schultze.  “Dey’re all dwins alike—­Dweedeldums und Dweedledeeses.”

Mr. Latham silently placed the fifth diamond on the table, and for a minute or more the five men stood still and gazed, first at the diamonds, then at one another, and then again at the diamonds.  Mr. Solomon, the crisply spoken head of Solomon, Berger and Company, broke the silence.

“These all came yesterday morning by mail, one to each of us just as the one came to you,” he informed Mr. Latham.  “Mr. Harris here, of Harris and Blacklock, learned that I had received such a stone, and brought the one he had received for comparison.  We made some inquiries together and found that a duplicate had been received by Mr. Stoddard, of Hall-Stoddard-Higginson.  The three of us came here to see if Mr. Schultze could give us any information, and he telephoned for you.”

Mr. Latham listened blankly.

“It’s positively beyond belief,” he burst out.  “What—­what does it mean?”

“Id means,” the German importer answered philosophically, “dat if diamonds like dese keep popping up like dis, dat in anoder d’ree months dey vill nod be vorth more as five cents a bucketful.”

The truth of the observation came to the four others simultaneously.  Hitherto there had been only the sense of wonder and admiration; now came the definite knowledge that diamonds, even of such great size and beauty as these, would grow cheap if they were to be picked out of the void; and realization of this astonishing possibility brought five shrewd business brains to a unit of investigation.  First it was necessary to find how many other jewelers had received duplicates; then it was necessary to find whence they came.  A plan was adopted, and an investigation ordered to begin at once.

“Dere iss someding back of id, of course,” declared Mr. Schultze. “Vas iss? Dey are nod being send for our healdh!”

During the next six days half a score of private detectives were at work on the mystery, with the slender clews at hand.  They scanned hotel registers, quizzed paper-box manufacturers, pestered stamp clerks, bedeviled postal officials, and the sum total of their knowledge was negative, save in the fact that they established beyond question that only these five men had received the diamonds.

And meanwhile the heads of the five greatest jewel houses in New York were assiduous in their search for that copperplate superscription in their daily mail.  On the morning of the eighth day it came.  Mr. Latham was nervously shuffling his unopened personal correspondence when he came upon it—­a formal white square envelope, directed by that same copperplate hand which had directed the boxes.  He dropped into his chair, and opened the envelope with eager fingers.  Inside was this letter: 

   My dear sir: