“This correspondence is of no consequence in itself, of course.  But it gives us this:  Carrier pigeons will only fly home, so if Mr. Wynne received a message by pigeon it means that at some time, within a week say, he has shipped that pigeon and perhaps others from the house in Thirty-seventh Street to that person who sent him the message.  If he sends messages to that person it means that he has received a pigeon or pigeons from that person within a week.  And how were these pigeons shipped?  In all probability, by express.  So, gentlemen, you see there ought to be a record in the express offices, which would give us the home town, even the name and address, of the person who now has the diamonds in his or her keeping.  Is that clear to all of you?”

“It is perfectly clear,” commented Mr. Laadham admiringly, while the German nodded his head in approval.

“And that is the clew we are working on at the moment,” the detective added.  “Three of my men are now searching the records of all the express companies in the city—­and there are a great many—­for the pigeon shipments.  If, as seems probable, this clew develops, it may be that we can place our hands on the diamonds within a few days.”

“I don’d d’ink I vould yust blace my hands on dem,” Mr. Schultze advised.  “Dey are his diamonds, you know, und your hands might ged in drouble.”

“I mean figuratively, of course,” the detective amended.

He stopped and drummed on his stiff hat with his fingers.  Again he glanced at the impassive face of Mr. Czenki with keen, questioning eyes; and for one bare instant it seemed as if he were trying to bring his memory to his aid.

“I’ve found out all about this man Wynne,” he supplemented after a moment, “but nothing in his record seems to have any bearing on this case.  He is an orphan.  His mother was a Van Cortlandt of old Dutch stock, and his father was a merchant downtown.  He left a few thousands to the son, and the son is now in business for himself with an office in lower Broad Street.  He is an importer of brown sugar.”

“Brown sugar?” queried Mr. Czenki quickly, and the thin, scarred face reflected for a second some subtle emotion within him.  “Brown sugar!” he repeated.

“Yes,” drawled the detective, with an unpleasant stare, “brown sugar.  He imports it from Cuba and Porto Rico and Brazil by the shipload, I understand, and makes a good thing of it.”

A quick pallor overspread Mr. Czenki’s countenance, and he arose with his fingers working nervously.  His beady eyes were glittering; his lips were pressed together until they were bloodless.

“Vas iss?” demanded Mr. Schultze curiously.

“My God, gentlemen, don’t you see?” the expert burst out violently.  “Don’t you see what this man has done?  He has—­he has—­”

Suddenly, by a supreme effort, he regained control of himself, and resumed his seat.