“There were difficulties, of course,” he said; “the crime was so carefully planned.  The little details, such as the footprints, the absence of any mud from the girl’s shoes in the carriage of the motor-car, the dinner at Annecy, the purchase of the cord, the want of any sign of a struggle in the little salon, were all carefully thought out.  Had not one little accident happened, and one little mistake been made in consequence, I doubt if we should have laid our hands upon one of the gang.  We might have suspected Wethermill; we should hardly have secured him, and we should very likely never have known of the Tace family.  That mistake was, as you no doubt are fully aware—­”

“The failure of Wethermill to discover Mme. Dauvray’s jewels,” said Ricardo at once.

“No, my friend,” answered Hanaud.  “That made them keep Mlle. Celie alive.  It enabled us to save her when we had discovered the whereabouts of the gang.  It did not help us very much to lay our hands upon them.  No; the little accident which happened was the entrance of our friend Perrichet into the garden while the murderers were still in the room.  Imagine that scene, M. Ricardo.  The rage of the murderers at their inability to discover the plunder for which they had risked their necks, the old woman crumpled up on the floor against the wall, the girl writing laboriously with fettered arms ‘I do not know’ under threats of torture, and then in the stillness of the night the clear, tiny click of the gate and the measured, relentless footsteps.  No wonder they were terrified in that dark room.  What would be their one thought?  Why, to get away—­to come back perhaps later, when Mlle. Celie should have told them what, by the way, she did not know, but in any case to get away now.  So they made their little mistake, and in their hurry they left the light burning in the room of Helene Vauquier, and the murder was discovered seven hours too soon for them.”

“Seven hours!” said Mr. Ricardo.

“Yes.  The household did not rise early.  It was not until seven that the charwoman came.  It was she who was meant to discover the crime.  By that time the motor-car would have been back three hours ago in its garage.  Servettaz, the chauffeur, would have returned from Chambery some time in the morning, he would have cleaned the car, he would have noticed that there was very little petrol in the tank, as there had been when he had left it on the day before.  He would not have noticed that some of his many tins which had been full yesterday were empty to-day.  We should not have discovered that about four in the morning the car was close to the Villa Rose and that it had travelled, between midnight and five in the morning, a hundred and fifty kilometres.”

“But you had already guessed ‘Geneva,’” said Ricardo.  “At luncheon, before the news came that the car was found, you had guessed it.”

“It was a shot,” said Hanaud.  “The absence of the car helped me to make it.  It is a large city and not very far away, a likely place for people with the police at their heels to run to earth in.  But if the car had been discovered in the garage I should not have made that shot.  Even then I had no particular conviction about Geneva.  I really wished to see how Wethermill would take it.  He was wonderful.”