"The mysterious Mr. Sabin is an unscrupulous French royalist who aids the German government in a conspiracy of war against England. His part in the plot is that of securing valuable papers recording the coast defenses of England, for which services he demands Germany's conquest of France and the restoration of the monarchy in the person of Prince Henri and his cousin, Helene of Bourbon"--Cumulative Book Review Digest, Vol. 1, no. 10, page 264.