"Oh, in the simplest possible fashion. I knew that Mr. Kesselbach was employing the Barbareux agency and that Lupin had called on him, pretending to come from the agency. I hunted in that direction and discovered that, when the indiscretion was committed to the prejudice of Mr. Kesselbach and of Barbareux, it could only have been to the advantage of one Jérôme, a friend of one of the clerks at the agency. If you had not ordered me to hustle things, I should have watched the messenger and caught Marco and then Lupin."
"You'll catch them, Lenormand, you'll catch them, I assure you. And we shall be assisting at the most exciting spectacle in the world: the struggle between Lupin and yourself. I shall bet on you."
The next morning the newspapers published the following letter:
"Open Letter to M. Lenormand, Chief of the Detective-service.
"All my congratulations, dear sir and dear friend, on your arrest of Jérôme the messenger. It was a smart piece of work, well executed and worthy of you.
"All my compliments, also, on the ingenious manner in which you proved to the prime minister that I was not Mr. Kesselbach's murderer. Your demonstration was clear, logical, irrefutable and, what is more, truthful. As you know, I do not kill people. Thank you for proving it on this occasion. The esteem of my contemporaries and of yourself, dear sir and dear friend, are indispensable to my happiness.
"In return, allow me to assist you in the pursuit of the monstrous assassin and to give you a hand with the Kesselbach case, a very interesting case, believe me: so interesting and so worthy of my attention that I have determined to issue from the retirement in which I have been living for the past four years, between my books and my good dog Sherlock, to beat all my comrades to arms and to throw myself once more into the fray.
"What unexpected turns life sometimes takes! Here am I, your fellow-worker! Let me assure you, dear sir and dear friend, that I congratulate myself upon it, and that I appreciate this favor of destiny at its true value.
"Arsène Lupin.