"Mr. Stapleton's. Look!" He drew toward him the sheet of paper. "Here," he placed the point of his pencil upon the black square which indicated the location of the banker's residence, "is the house. The north window of a room on the top floor commands a view of the Avenue du Bois de Boulogne, from a point some 500 feet west of the Arc de Triomphe, to where it intersects the Avenue Malakoff. Beyond there, the view is interrupted. In fact, the trees along the Avenue du Bois de Boulogne are to some extent an obstruction; but at the crossing with the Avenue Malakoff there is a wide and uninterrupted view."
"But a confederate in Monsieur Stapleton's own house?"
"Yes. The chauffeur, François."
"You astonish me, Monsieur. We have suspected the fellow, it is true. The very room of which you speak has been searched. We found nothing. How do you know that what you say is true?"
"Never mind how I know it—now. The point is this—François, I fully believe, will be in that room, tonight, at eight o'clock, watching carefully the automobiles which pass the intersection of the Avenue Malakoff—"
"Not necessarily, Monsieur. We can easily prevent it, by placing him under arrest."
"That is exactly what we must not do. Don't you see, it is absolutely necessary, for the recovery of Mr. Stapleton's child, that the signals go through uninterrupted?"
"Of course, I had forgotten that. And these signals?"
"Naturally I cannot tell—yet. I think, however, that the automobile for which François will be looking will show a brilliant blue light, while crossing the Avenue Malakoff. That is, of course, if our friend the kidnapper gets safely away, without being pursued."
"And otherwise?"