"Hullo," he cried, "what's this?" and pulling out a pocket magnifier he scrutinized a small red spot a short distance above the wrist. "Come here, Villebois, and tell me what you think of this."

Villebois took the magnifier out of Riche's hand, and carefully examined the spot. He looked up in an enquiring manner as if he expected Riche to speak for him.

"Well, what do you make of it?" said Riche as he looked at him with a peculiar expression and curl of the mouth which he always wore when he knew beforehand what the answer would be.

"Tell me, what is it?" he repeated as Villebois hesitated.

"I think it is a hypodermic puncture. Isn't that your opinion?"

"I don't think anything about it, I am sure of it; and what's more I feel convinced it was made with the needle found on the floor. The rascal was evidently injecting the poison at the very moment when we interrupted him as he was trying to open the door. Don't you agree with me?"

"Yes, you are perfectly right," said Villebois, nodding his head. "How fortunate you were to find the syringe, and half full of the poison too. Don't lose the fluid whatever you do. It appears to me to be the key to the whole mystery."

"You trust me," said Riche, "I am not going to let the matter drop, my little bottle will bring the scoundrel to the guillotine yet." Meanwhile the firemen had arrived, and as there was an abundance of water, the fire was soon under control. Although the contents of Riche's room were destroyed, no damage was done outside it except by the water. On entering the room the firemen smelt the pungent odour of burnt naphtha, and a few shavings still glowing with the heat were to be seen in a corner of the room.

"Ei! Ei! this is the work of an incendiary," said one of the firemen. "Regardez-la, monsieur," he said to Villebois whom he knew by sight, holding up some of the half-burnt shavings, "don't you smell the naphtha?"