The Passenger from Calais

(from contemporary publisher's advert)
A bright, quickly moving detective storytelling of the adventures which befell a mysterious lady flying from Calais through France into Italy, closely pursued by detectives. Her own quick wits, aided by those of a gallant fellow passenger, give the two officers an unlooked-for and exciting "run for their money." One hardly realized till now the dramatic possibilities of a railway train, and what an opportunity for excitement may be afforded by a joint railway station for two or more roads.
It is a well-planned, logical detective story of the better sort, free from cheap sensationalism and improbability, developing surely and steadily by means of exciting situations to an unforeseen and satisfactory ending.

The author was a military officer and prison official who published more than 60 books, including this one -- a mystery with characters tearing up and down across Europe that somehow manages to be both slow-moving and not at all mysterious. Not to mention the deux ex machina ending. Multiple narrators are always fun, though, the heroine is smart and competent, and there's a lot of description of trains, station protocols and personnel, and various station-adjacent hotel districts that might be of interest. The author says in the foreword that "I travelled from Calais to Basle [sic] by the Engadine Express in the latter end of July, 1902, when my wife and myself were the only passengers." So it is to be presumed that the reflections on the character of Swiss railway workers, etc. that his characters voice were his own.