As to him, Mrs. Spencer was not concerned.  His possession of the letter, under such circumstances, effectually closed his mouth; if he happened to know for whom the letter was intended, his mouth was closed all the tighter.  It was a rule of the diplomatic game never to reveal, even to an ally, what you know; tomorrow the ally may be the enemy.  Harleston might yield the letter to superior force or to trickery, but he would never babble of it.

The door opened to admit Banks.

“The detective has nothing whatever as to Madame Cuthbert,” he explained.  “He says she is apparently a lady, and nothing has occurred to bring her under his notice.  For the same reason, no list of her callers has been made—­though the desk thinks that they have been comparatively few.  The man with whom she dined this evening is a Mr. Rufus Martin.  He has been with her several times.  He is a guest of the hotel—­room No. 410.”

“Can you have her apartment and Martin’s looked over without exciting suspicion?”

“I think we can manage it,” Banks responded.  “Indeed, I think we can manage to have all the rooms inspected; I have already told the detective what we suspect, and he has put on an employee’s uniform and with a basket of electric bulbs is now testing the lights in every occupied room.  The moment he finds Mrs. Clephane, or anything that points to her, he will advise us.”

“Good!” said Harleston.  “Meanwhile, I’ll have another look in Peacock Alley.”

He was aware that he was acting on a pure hunch.  He realized that his theory of Mrs. Clephane’s imprisonment in the house was most inconsistent with the facts.  Why did they release her last night, if they were fearful of her communicating to the French Ambassador the loss of the letter?  And why should they take her again this evening?  It was all unreasonable; yet reason does not prevail against a hunch—­even to a reasoning man, who is also a diplomat.

He sauntered along the gay corridor bowing to those he knew.  As he faced about to return, he saw Madeline Spencer, alone, bearing down upon him.

The moment their eyes met, she signalled a glad smile and advanced with hands extended.

“Why, Guy!” she exclaimed.  “What a surprise this is!”

“And what a charming pleasure to me, Madeline,” he added, taking both her hands and holding them.  “I thought you were in Paris; indeed, I thought you would never leave the City of Boulevards.”

“So did I, yet here I am; yet not for long, I trust, Guy, not for long.”

“America’s misfortune,” he whispered.

“Or fortune!” she laughed.  “It’s merely a matter of viewpoint.  To those who have knowledge of the comparatively recent past, Madeline Spencer may be a persona non.  However—­” with a shrug of her shapely shoulders and an indifferent lift of her fine hands.  “Won’t you sit down, Mr. Harleston; that is, if you’re not afraid for your reputation.  I assume that here you have a reputation to protect.”