“That is true,” said the doctor.  “Look!” and he took up from the floor by his knee the weapon which had caused Marthe Gobin’s death.  It was nothing but an ordinary skewer with a ring at one end and a sharp point at the other, and a piece of common white firewood for a handle.  The wood had been split, the ring inserted and spliced in position with strong twine.  It was a rough enough weapon, but an effective one.  The proof of its effectiveness lay stretched upon the floor beside them.

Hanaud gave it to the manager of the hotel.

“You must be very careful of this, and give it as it is to the police.”

Then he bent once more over Marthe Gobin.

“Did she suffer?” he asked in a low voice.

“No; death must have been instantaneous,” said the doctor.

“I am glad of that,” said Hanaud, as he rose again to his feet.

In the doorway the driver of the cab was standing.

“What has he to say?” Hanaud asked.

The man stepped forward instantly.  He was an old, red-faced, stout man, with a shiny white tall hat, like a thousand drivers of cabs.

“What have I to say, monsieur?” he grumbled in a husky voice.  “I take up the poor woman at the station and I drive her where she bids me, and I find her dead, and my day is lost.  Who will pay my fare, monsieur?”

“I will,” said Hanaud.  “There it is,” and he handed the man a five-franc piece.  “Now, answer me!  Do you tell me that this woman was murdered in your cab and that you knew nothing about it?”

“But what should I know?  I take her up at the station, and all the way up the hill her head is every moment out of the window, crying, ‘Faster, faster!’ Oh, the good woman was in a hurry!  But for me I take no notice.  The more she shouts, the less I hear; I bury my head between my shoulders, and I look ahead of me and I take no notice.  One cannot expect cab-horses to run up these hills; it is not reasonable.”  “So you went at a walk,” said Hanaud.  He beckoned to Ricardo, and said to the manager:  “M.  Besnard will, no doubt, be here in a few minutes, and he will send for the Juge d’Instruction.  There is nothing that we can do.”

He went back to Ricardo’s sitting-room and flung himself into a chair.  He had been calm enough downstairs in the presence of the doctor and the body of the victim.  Now, with only Ricardo for a witness, he gave way to distress.

“It is terrible,” he said.  “The poor woman!  It was I who brought her to Aix.  It was through my carelessness.  But who would have thought—?” He snatched his hands from his face and stood up.  “I should have thought,” he said solemnly.  “Extraordinary daring—­ that was one of the qualities of my criminal.  I knew it, and I disregarded it.  Now we have a second crime.”

“The skewer may lead you to the criminal,” said Mr. Ricardo.

“The skewer!” cried Hanaud.  “How will that help us?  A knife, yes—­ perhaps.  But a skewer!”