Half-Moon Street was bathed in tropical sunlight. Dr. Cairn, with his hands behind him, stood looking out of the window. He turned to his son, who leant against a corner of the bookcase in the shadows of the big room.  
"Hot enough for Egypt, Rob," he said.
 
Robert Cairn nodded.
 
"Antony Ferrara," he replied, "seemingly travels his own atmosphere with him. I first became acquainted with his hellish activities during a phenomenal thunderstorm. In Egypt his movements apparently corresponded with those of the Khamsîn. Now,"—he waved his hand vaguely towards the window—"this is Egypt in London."
 
"Egypt is in London, indeed," muttered Dr. Cairn. "Jermyn has decided that our fears are well-founded."
 
"You mean, sir, that the will—?"
 
"Antony Ferrara would have an almost unassailable case in the event of—of Myra—"
 
"You mean that her share of the legacy would fall to that fiend, if she—"
 
"If she died? Exactly."
 
Robert Cairn began to stride up and down the room, clenching and unclenching his fists. He was a shadow of his former self, but now his cheeks were flushed and his eyes feverishly bright.
 
"Before Heaven!" he cried suddenly, "the situation is becoming unbearable. A thing more deadly than the Plague is abroad here in London. Apart from the personal aspect of the matter—of which I dare not think!—what do we know of Ferrara's activities? His record is damnable. To our certain knowledge his victims are many. If the murder of his adoptive father, Sir Michael, was actually the first of his crimes, we know
[147]
of three other poor souls who beyond any shadow of doubt were launched into eternity by the Black Arts of this ghastly villain—"
 
"We do, Rob," replied Dr. Cairn sternly.
 
"He has made attempts upon you; he has made attempts upon me. We owe our survival"—he pointed to a row of books upon a corner shelf—"to the knowledge which you have accumulated in half a life-time of research. In the face of science, in the face of modern scepticism, in the face of our belief in a benign God, this creature, Antony Ferrara, has proved himself conclusively to be—"
 
"He is what the benighted ancients called a magician," interrupted Dr. Cairn quietly. "He is what was known in the Middle Ages as a wizard. What that means, exactly, few modern thinkers know; but I know, and one day others will know. Meanwhile his shadow lies upon a certain house."
 
Robert Cairn shook his clenched fists in the air. In some men the gesture had seemed melodramatic; in him it was the expression of a soul's agony.
 
"But, sir!" he cried—"are we to wait, inert, helpless? Whatever he is, he has a human body and there are bullets, there are knives, there are a hundred drugs in the British Pharmacopœia!"
 
"Quite so," answered Dr. Cairn, watching his son closely, and, by his own collected manner, endeavouring to check the other's growing excitement. "I am prepared at any personal risk to crush Antony Ferrara as I would crush a scorpion; but where is he?"
 
Robert Cairn groaned, dropping into the big red-leathern armchair, and burying his face in his hands.
 
"Our position is maddening," continued the elder man. "We know that Antony Ferrara visits Mr. Saunderson's house; we know that he is laughing at our vain attempts to trap him. Crowning comedy of all, Saunderson does not know the truth; he is not the type of man who could ever understand; in fact we dare not tell him—and we dare not tell Myra. The result is that those whom we would protect, unwittingly are working against us, and against themselves."
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"That perfume!" burst out Robert Cairn; "that hell's incense which loads the atmosphere of S............