The House of Evil by William Le Queux

Lydon might not be able to lay claim to any remarkable brilliance of intellect. At Harrow and Oxford his progress had been steady and respectable, but he had not distinguished himself like his friend Craig, for instance, to whom the acquisition of knowledge was an easy task, whose mental alertness was the delight of his masters and tutors.

But he was a shrewd young fellow, and endowed with a considerable fund of common-sense. He also possessed a dogged spirit of determination. When he once took a thing up he persevered with it, and was not easily daunted by obstacles. There were, at the present moment, two things he was resolved to find out by some means or other -- the precise nature of Stormont's business and the life history of the dark, handsome girl known as Zillah Mayhew.