"I see nothing, nothing at all," he replied. "Look here, monsieur," said Villebois, pointing to a little swollen spot just above the wrist of the left arm. "Do you see that?" Monsieur Biron looked at it carefully, and shrugged his shoulders. "Ce n'est rien, monsieur; it is only a mosquito bite." Villebois examined it with a pocket magnifier, and gently squeezed it. A drop of glistening fluid came out tinged with blood. The commissaire at once became intensely interested. "Lend me the glass," he cried, and impatiently taking it from Villebois, he carefully examined the spot. "H'm," he muttered, "the puncture is certainly too large for an insect to make. Can you account for it, doctor?" he said, relinquishing for the first time his authoritative tone. "I can, but Dr. Riche whom you saw just now can tell you more about it than I can. It was Dr. Riche who told me that he had heard someone moving about the room, and when the doctor ran to the door, before he could open it wide enough to see who was inside, it was violently shut in his face and locked. Dr. Riche and myself together managed to force the door, only to find that the rascal had escaped. Riche raced after him, but the fellow was too quick, and before Riche could get near enough to recognise him, he had disappeared in a fiacre." "Mon Dieu, but why didn't you tell me all this before?" asked M. Biron. "Monsieur, I could not, as the whole affair has altogether unnerved me. Besides, Dr. Riche was about to tell you, but you stopped him, if you remember, and threatened to arrest him if he spoke." The little man stamped on the ground with vexation and chagrin. "Well, well," he replied somewhat mollified, "I trust it is not too late yet; bring him here at once." Villebois opened the door and beckoned to him to come in. Riche had taken the commissaire's conduct so much to heart that at first he refused to answer. "A thousand pardons, M. le docteur, for appearing so rude," said the commissaire in a very apologetic tone, "but I understand that you are able to give some clue to this assassination?" Dr. Riche, seeing that M. Biron's apology was sincere, slowly thawed and became more amiable. "Yes, monsieur," he replied, "I came downstairs during the fire to look after the professor, who was fast asleep on a couch, and just as I was about to enter the chamber, the door was shut in my face and locked. When I entered the room the bird had flown, but I picked up a hypodermic syringe half full of liquid, from the floor." "But didn't you try to find the fellow?"