Her Royal Highness by William Le Queux

At their feet, winding its way for thousands of miles between limitless areas of sand, its banks lined for narrow distances with green fields and the habitations of men, flowed dark and wondrous the one thing that makes human life possible in all the lands of the Sudan and of Egypt -- flowed from sources that for ages were undiscovered, and which even in this day of boasted knowledge are yet incompletely known -- the Nile.

In the lazy indolence of that sun-baked land of silence, idleness and love, affection is quickly cultivated, as the fast-living set who go up there each winter know well. Hubert Waldron, man of the world that he was, had watched and knew. He stood there, however, dumbfounded, for there was now presented a very strange and curious state of affairs. Lola, the dark-eyed girl who had enchanted him and held him by the great mystery which surrounded her, was now revealed keeping tryst with a stranger -- a mysterious Frenchman who had come up from the blazing Sudan -- a man who had come from nowhere.