The Pauper of Park Lane by William le Queux

Four nights later Max and Charlie alighted from the Scotch express at Euston on their return to London to make investigation.

Next morning Rolfe went as usual to Park Lane, and spent some hours attending to the old man's correspondence. The excuse Charlie made for his absence was that he had been away in an endeavour to find his sister, whereat the millionaire merely grunted in dissatisfaction. Both Charlie and Max were full of sorrow and anxiety on Marion's behalf. What had befallen her they dreaded to guess. She had left Oxford Street, and from that moment had been swallowed in the bustling vortex of our great cruel London, the city where money alone is power and where gold can purchase everything, even to the death of one's enemy. Perhaps the poor girl had met with some charitable woman who had taken her in and given her shelter; but more probable, alas! she was wandering hungry and homeless, afraid to face the shame of the dastardly charge against her -- the charge that to neither her brother nor her lover none would name.