The mysterious stranger, who had not lost a word of this conversation, heard the door of the vestibule close, then the gravel of the garden crunch under the feet of the girl coming down the path. Very soon the gate of the garden grated on its badly oiled hinges, and then the elegant outline of a young girl was visible on the badly lighted pavement. She was walking fast....
The stranger remained stationary until the girl had gone some way; then pressing against the wall, concealing his movements with practised ability, he followed her at a discreet distance....
"There can be no doubt about it," he murmured. "I recognised her voice directly!... It's the very deuce!... It's going to complicate matters!... A lover's meeting? Not likely!... She must be going to the post, as she said.... She will return in about a quarter of an hour, and then ... then!..."
The girl was far from suspecting that she was being followed. She had walked down rue Mozart, turned into rue Poussin, posted her letter, and then walked quietly back to the house.
The stranger had not followed her into the more frequented streets: he awaited her return in a dark and deserted side street. When she came into view again, he sighed a sigh of great satisfaction.
"Ah, there is the dear child!... That's all right.... Now we shall have some fun!... or, rather, I shall!"
Anyone seeing his face, whilst making these significant exclamations, would have been frightened by his sneering chuckle, his hideous grin.
A few minutes later, the girl re-entered the little garden of the house in the rue Raffet. A stout woman opened to her ring.
"Ah, there you are, darling." There was relief in her tone.
"Yes, here I am, safe and sound, madame!"