Keeper of the Keys – Earl Derr Biggers – Platanus Publishing

“Charlie dropped into a chair and, for lack of anything better to do, studied his fellow traveler, some distance down the aisle. The man was a lean, rather distinguished-looking foreigner of some sort—probably a Latin, Chan thought. His hair was as black and sleek as the detective’s, save where it was touched with gray over the ears. His eyes were quick and roving, his thin hands moved nervously about, he sat on the edge of his chair, as though his stay on the train was but a brief interlude in an exciting life. When the steward returned with a package of cigarettes on a silver tray and got his money and tip from the other passenger, Chan beckoned to him. The boy was at his side in an instant.”