Under these windows there was no disturbance of the ground, and a careful investigation showed conclusively that the only entrance used had been the glass doors of the salon facing the drive.

To that spot, then, they returned.

There were three sets of footmarks upon the soil.

One set ran in a distinct curve from the drive to the side of the door, and did not cross the others.
"Those," said Hanaud, "are the footsteps of my intelligent friend, Perrichet, who was careful not to disturb the ground." Perrichet beamed all over his rosy face, and Besnard nodded at him with condescending approval.
"But I wish, M.le Commissaire"-- and Hanaud pointed to a blur of marks--"that your other officers had been as intelligent.

Look! These run from the glass door to the drive, and, for all the use they are to us, a harrow might have been dragged across them." Besnard drew himself up.
"Not one of my officers has entered the room by way of this door.