“The pickpockets on _trains de luxe_,” he declared, “have this much in common with the officers of the Criminal Investigation Department, that they are usually ill-shod. With one class as with the other, there is nothing, speaking generally, to find fault with in the get-up. Hat from the best maker, clothes of an irreproachable cut, tasteful necktie, well-kept hands, everything proclaims the man of the world; but there is a small detail, a grain of sand, the proverbial grain of sand that throws the best adjusted machine out of gear, and that grain of sand is nothing more nor less than the footwear ...” Tom Bob broke off, and turning to the young Frenchman who was listening with a highly quizzical smile: “Sir,” he asked, “will you allow me to ask you a question—what is your profession?” At this direct and almost peremptory demand, the youth blushed in some embarrassment. The answer came in a dull, heavy voice: “Why, sir, if I chose not to answer, I should be within my rights and would tell you nothing ... But there, I have nothing to hide—I am a student, a medical student, sir.” The young man was evidently annoyed and turning his back on his questioner, he left the corridor. Suddenly, a few moments after this, the train was plunged into utter darkness. The track, after running for some distance alongside the Seine near Bonnières, had entered a tunnel. The Princess Danidoff’s anxious voice was heard complaining: “Why isn’t the carriage lighted? How very extraordinary!” Tom Bob gave a sharp order: “Have a care, ladies; look out, gentlemen; this darkness is altogether abnormal; it is due to no negligence on the part of the Company, but undoubtedly to the act of some miscreant; guard your jewelry, watch your pockets.” A few moments that seemed like hours, and then, issuing suddenly from the bowels of the earth, the train regained the light of day and sped on across the open country. Mrs. Bigelow gave a cry; her reticule had vanished. “My bag,” she groaned, “what has become of my little bag? Why, it’s appalling, verily this land of France is nothing but a den of thieves.” Mr. Van Buren remarked: “I thought just now Mr. Bob was joking, but I am beginning to think he was perfectly serious.” “By Gad!” exclaimed Ascott, who could _not_ believe his pocket-book had really vanished and had just finished turning his portmanteau upside down, “by Gad! I think I ought to know something about it.” The American detective was biting his lips with annoyance; mechanically he lit a cigarette, then tossed it away, only to light another. A ticket collector passed along the train, shouting “tickets! tickets, please!” But two passengers found themselves unable to produce theirs—Ascott and Mrs. Bigelow.