Why else should he have returned except to put back the car?
Consider! The petrol is taken from tins which Servettaz might never have touched for a fortnight, and by that time he might, as he said, have forgotten whether he had not used them himself.

I had this possibility in my mind when I put the questions to Servettaz about the petrol which the Commissaire thought so stupid.

The utmost care is taken that there shall be no mould left on the floor of the carriage.

The scrap of chiffon was torn off, no doubt, when the women finally left the car, and therefore not noticed, or that, too, would have been removed.

That the exterior of the car was dirty betrayed nothing, for Servettaz had left it uncleaned." Hanaud leaned back and, step by step, related the journey of the car.
"The man leaves the gate open; he drives into Geneva the two women, who are careful that their shoes shall leave no marks upon the floor.