As Loupart, followed by Fandor, was about to enter the Cité Frochot, an exclamation made them both turn. Fandor perceived a poorly dressed man anxiously searching for something in the gutter. A curious crowd had instantly collected, and word was passed round that the lost object was a twenty-five-franc gold piece. Fandor, joining the crowd, was pushed close to the man, who quickly whispered: "Idiot! Keep out of the Cité." The owner of the gold piece was no other than the detective. Then, under cover of loud complaint, Juve muttered to Fandor, "Let him go! Watch the entrance to the Cité!" "But," objected Fandor in the same key, "what if I lose sight of him?" "No fear of that. The doctor's house is the second on the right." The hooligan, who had for a moment drawn near the crowd, was now heading straight for the Cité. Juve went on: "In a quarter of an hour at the latest join me again, 27 Rue Victor Massé." "And if Loupart should enter the Cité in the meantime?" "Come straight back to me." Fandor was moving off when Juve addressed him out loud: "Thank you, kind gentlemen! But as you are so charitable, give me something more for God's sake." The other drew near the pretended beggar and Juve added: "If anyone questions you as you pass through, say you are going to Omareille, the decorator's; you'll find me on the stairs." Some moments later the little crowd had melted away and a policeman, arriving as usual too late, wondered what had been going on. Fandor carried out Juve's instructions to the letter. Hiding behind a sentry box he kept an eye on the doctor's house, but nothing out of the way happened. Loupart had vanished, although he was probably not far away. When the fifteen minutes were up Fandor left his post and entered No. 27 Rue Victor Massé. As he reached the third floor he heard Juve's voice: "Is that you, lad?" "Yes." "The porter didn't question you?" "I've seen no one." "All right, come up here." Juve was seated at a hall window examining Doctor Chaleck's house through a field glass. "You've not seen Loupart go in?" he inquired as Fandor joined him. "Not while I was on watch." "It's well to know one's Paris and have friends everywhere, isn't it?" continued Juve. "It occurred to me quite suddenly that this might be an excellent place from where to follow citizen Loupart's doings. You would have spoiled everything if you had followed him into the Cité. That's why I devised my little scheme to hold you back." "You are right," admitted Fandor, who, the next moment, gave a jump as Juve's hand gripped him hard. "Look, Fandor! The bird is going into the cage!" The journalist, excited, saw a figure already familiar to him in the act of slipping into the little garden which separated Dr. Chaleck's house from the main thoroughfare. The detective went on: "There he goes, skirting the house until he reaches the little door hidden in the wall. What's he up to now? Ah! He's fumbling in his pocket. False keys, of course."