Then, in an _arabiyeh_ just driving off, he detected the hideous mask. Hatless as he was, he ran down the steps and threw himself into another. The carriage-controller was in attendance, and Cairn rapidly told him to instruct the driver to follow the _arabiyeh_ which had just left. The man lashed up his horses, turned the carriage, and went galloping on after the retreating figure. Past the Esbekiya Gardens they went, through several narrow streets, and on to the quarter of the Muski. Time after time he thought he had lost the carriage ahead, but his own driver's knowledge of the tortuous streets enabled him always to overtake it again. They went rocking along lanes so narrow that with outstretched arms one could almost have touched the walls on either side; past empty shops and unlighted houses. Cairn had not the remotest idea of his whereabouts, save that he was evidently in the district of the bazaars. A right-angled corner was abruptly negotiated--and there, ahead of him, stood the pursued vehicle! The driver was turning his horses around, to return; his fare was disappearing from sight into the black shadows of a narrow alley on the left. Cairn leaped from the _arabiyeh_, shouting to the man to wait, and went dashing down the sloping lane after the retreating figure. A sort of blind fury possessed him, but he never paused to analyse it, never asked himself by what right he pursued this man, what wrong the latter had done him. His action was wholly unreasoning; he knew that he wished to overtake the wearer of the mask and to tear it from his head; upon that he acted! He discovered that despite the tropical heat of the night, he was shuddering with cold, but he disregarded this circumstance, and ran on. The pursued stopped before an iron-studded door, which was opened instantly; he entered as the runner came up with him. And, before the door could be reclosed, Cairn thrust his way in. Blackness, utter blackness, was before him. The figure which he had pursued seemed to have been swallowed up. He stumbled on, gropingly, hands outstretched, then fell--fell, as he realised in the moment of falling, down a short flight of stone steps. Still amid utter blackness, he got upon his feet, shaken but otherwise unhurt by his fall. He turned about, expecting to see some glimmer of light from the stairway, but the blackness was unbroken. Silence and gloom hemmed him in. He stood for a moment, listening intently. A shaft of light pierced the darkness, as a shutter was thrown open. Through an iron-barred window the light shone; and with the light came a breath of stifling perfume. That perfume carried his imagination back instantly to a room at Oxford, and he advanced and looked through into the place beyond. He drew a swift breath, clutched the bars, and was silent--stricken speechless.