The magistrate adjusted his eyeglass and, looking at the place indicated by the detective, saw a little black stain; he wetted his finger, rubbed it on the spot, and then, holding up his hand, observed that the tip of his finger was stained red. "It is blood," he muttered. "Yes, blood," said Juve, "and I gather from this that the story of the blood-stained towel which M. Rambert senior found among his son's things, and the sight of which so greatly impressed Mlle. Thérèse, was not an invention on that young lady's part, but really existed; and it forms the most damning evidence possible against the young man. He obviously washed his hands after the crime in the water from the tap over this wash-hand basin here, but one drop of blood falling on the towel and dripping on to the floor has been enough to give him away." The magistrate nodded. "It is conclusive," he said. "You have just proved to demonstration, M. Juve, that Charles Rambert is the guilty party. It is beyond argument. It is conclusive--conclusive!" There were a couple of seconds of silence, and then Juve suddenly said "No!" "No!" he repeated; "it is quite true that we can adduce perfectly logical arguments to show that the murder was committed by some member of the household and that, therefore, Charles Rambert is the only possible culprit; but we can adduce equally logical arguments to show that the crime was committed by some person who got in from outside: there is nothing to prove that he did not walk into the house through the front door." "The door was locked," said the magistrate. "That's nothing," said Juve with a laugh. "Don't forget that there isn't such a thing as a real safety lock nowadays--since all locks can be opened with an outside key. If I had found one of the good old-fashioned catch locks on the door, such as they used to make years ago, I should have said to you: nobody got in, because the only way to get through a door fastened with one of those locks is to break the door down. But here we have a lock that can be opened with a key. Now the key does not exist of which one cannot get an impression, and there is not such a thing as an impression from which one cannot manufacture a false key. The murderer could easily have got into the house with a duplicate key." The magistrate raised a further objection. "If the murderer had got in from outside he would inevitably have left some traces round about the château, but there aren't any." "Yes there are," Juve retorted. "First of all there is this piece of an ordnance map which I found yesterday between the château and the embankment." He took it from his pocket as he spoke. "It is an odd coincidence that this scrap shows the neighbourhood of the château of Beaulieu." "That doesn't prove anything," said the magistrate. "To find a piece of a map of our district in our district is the most natural thing possible. Now if you were to discover the rest of this map in anybody's possession, then----"