Sax Rohmer 
Brood of the Witch-Queen [EPUB ebook] 

"Brood of the Witch Queen" is a 1918 supernatural novel by Arthur Henry Sarsfield Ward, known better under his pseudonym, Sax Rohmer. Sax Rohmer was a prolific eng novelist. He is best remembered for his series of novels featuring the master criminal Dr. Fu Manchu. The story deals with Robert Cairn and his suspicions of Antony Ferrara, the adopted son of an old friend and colleague of Robert’s father, Dr Bruce Cairn, of infernal magic and supernatural influence. (Excerpt from Wikipedia)