"You know, my boy," he said, "I should never have allowed Eileen" (his daughter) "to remain in Cairo, if I had foreseen this change in the weather. This infernal wind, coming right through the native town, is loaded with infection." "Has it affected her, then?" asked Sime anxiously. "She nearly fainted in the ball-room," replied the Colonel. "Her mother took her home half an hour ago. I looked for you everywhere, but couldn't find you." "Quite a number have succumbed," said Sime. "Eileen seemed to be slightly hysterical," continued the Colonel. "She persisted that someone wearing a crocodile mask had been standing beside her at the moment that she was taken ill." Sime started; perhaps Cairn's story was not a matter of imagination after all. "There is someone here, dressed like that, I believe," he replied, with affected carelessness. "He seems to have frightened several people. Any idea who he is?" "My dear chap!" cried the Colonel, "I have been searching the place for him! But I have never once set eyes upon him. I was about to ask if _you_ knew anything about it!" Sime returned to the table where Cairn was sitting. The latter seemed to have recovered somewhat; but he looked far from well. Sime stared at him critically. "I should turn in," he said, "if I were you. _Khamsin_ is playing the deuce with people. I only hope it does not justify its name and blow for fifty days." "Have you seen the man in the mask!" asked Cairn. "No," replied Sime, "but he's here alright; others have seen him." Cairn stood up rather unsteadily, and with Sime made his way through the moving crowd to the stairs. The band was still playing, but the cloud of gloom which had settled upon the place, refused to be dissipated. "Good-night, Cairn," said Sime, "see you in the morning." Robert Cairn, with aching head and a growing sensation of nausea, paused on the landing, looking down into the court below. He could not disguise from himself that he felt ill, not nervously ill as in London, but physically sick. This superheated air was difficult to breathe; it seemed to rise in waves from below. Then, from a weary glancing at the figures beneath him, his attitude changed to one of tense watching. A man, wearing the crocodile mask of Set, stood by a huge urn containing a palm, looking up to the landing! Cairn's weakness left him, and in its place came an indescribable anger, a longing to drive his fist into that grinning mask. He turned and ran lightly down the stairs, conscious of a sudden glow of energy. Reaching the floor, he saw the mask making across the hall, in the direction of the outer door. As rapidly as possible, for he could not run, without attracting undesirable attention, Cairn followed. The figure of Set passed out on to the terrace, but when Cairn in turn swung open the door, his quarry had vanished.