Suddenly Mohammed Abbas closed the door upon the stairs, and sharply clapped his hands.  In all lands where Allah is worshiped, clapping of the hands is a signal of summons.  Thrusting his hand into the pocket where he had stored an automatic pistol, Karyl found it empty, and remembered that on the stairway the merchant had apologized for jostling him.  Then simultaneously the two opposite doors opened and framed against their light a momentary picture of crowding Arabs.

* * * * *

Outside, Benton had been searching.  First he had felt only annoyance for a chance separation, but when ten minutes of futile wandering had lengthened to fifteen, annoyance gave way to fear, and fear to panic.  A dozen tragic stories of mysterious disappearances in Stamboul crowded like nightmares upon his memory.  At last, standing bewildered in the street, he caught sight of a familiar figure; a figure that filled him with astonishment and delight.

Colonel Von Ritz had left Cairo to return to Puntal.  Now here he was in a crooked Stamboul street, appearing without warning, but with his almost uncanny faculty for being at the right spot when needed.  He shouldered his way to the side of the officer.

Though the two men had parted several weeks before, the Galavian greeted the other only with a formal bow, and an abrupt question.  “Where are they?”

“I have lost them,” replied Benton.  He rapidly sketched the events of the last half-hour, and confessed his own apprehensions.

With evidence of neither anxiety nor interest, Von Ritz listened, and replied with a second question.  “Have you seen Martin?”

Benton gave a palpable start.  “Martin!” he ejaculated.  “Is Martin in Constantinople?”

For reply Von Ritz permitted himself the rare indulgence of a smile.

“Martin is here,” he said briefly.

“And you—?”

As he spoke the figure of Martin himself emerged from a shop a few paces ahead, and without a backward glance cut diagonally across the narrow street to disappear into the doorway of the curio shop which is kept by Mohammed Abbas.

When, after being cut off and delayed for some minutes by a passing donkey train, Von Ritz and Benton entered the place, they found it empty except for a native salesman, but as the Galavian paused to make a trivial purchase his listening ear caught a sound above.  Without hesitation, he wheeled and mounted the stairs with Benton close at his heels.  Behind him the shop-clerk stood irresolute—­taken aback, with a vague consciousness that he should have devised a way to stop this gigantic Infidel.  Assuredly the master would be angry.  Orders had been explicitly given to allow no one to climb those steps to-day without permission.

While Cara and Karyl had been on the second floor, a heavy Osmanli, wearing the Sultan’s uniform, had stood in the center of the room above, looking about with keen, pig-like eyes, as he gave rapid commands to a half dozen Arabs of villainous visage.