“Ah, now I see!” Mme. Laurent-Desrousseaux exclaimed, not at all unsusceptible to the turn of Sir Clinton's phrase. “You mean the difference between the cab-horse and the stepper?” “Exactly,” Sir Clinton agreed with an impassive face. Armadale was still puzzling over the two footprints. Mme. Laurent-Desrousseaux, evidently wearying of standing with one foot off the ground, recovered her shoe from him and slipped it on again. Sir Clinton took pity on his subordinate. “Here's the explanation, inspector. When you walk in sand, you put down your heel first. But as the sand's soft, your heel goes forward and downward as you plant your foot. Then, as your body moves on, your foot begins to turn in the sand; and when you've come to the end of your step, your toe also is driven downwards; but instead of going _forward_, like your heel, it slips backward. The result is that in the impression the heel is too far forward, whilst the toe is in the rear of the true position—and that means an impression shorter than the normal. On the sand, your foot really pivots on the sole under the instep, instead of on heel and toe, as it does on hard ground. If you look at these impressions, you'll find quite a heap of sand under the point where the instep was; whilst the heel and toe are deeply marked owing to each of them pivoting on the centre of the shoe. See it?” The inspector knelt down, and Wendover followed his example. They had no difficulty in seeing Sir Clinton's point. “Of course,” the chief constable went on, “in the case of a woman's shoe, the thing is even more exaggerated owing to the height of the heel and the sharpness of the toe. Haven't you noticed, in tracks on the sand, how neat any woman's prints always look? You never seem to find the impression of a clumsy foot, simply because the impression is so much smaller than the real foot. Clear enough, isn't it?” “You are most ingenious, Sir Clinton,” Mme. Laurent-Desrousseaux commented. “I am very glad indeed that I have not you against me.” Sir Clinton turned the point. “The inspector will bring you a copy of the evidence you have so kindly given us, madame, and you will do us the favour to sign it. It is a mere formality, that; but we may need you as a witness in the case, you understand?” Rather ungraciously, Mme. Laurent-Desrousseaux agreed. It was evident that she had hoped to escape giving evidence in court. “I do not desire to offer testimony against the young Madame Fleetwood if it could be averted,” she said frankly. “She was good to me once or twice; very gentle, very kind—not like the others in the hotel.” The inspector shrugged his shoulders, as though the matter were out of his hands; but he made no reply. “You will, of course, say nothing about this to anyone, madame,” Sir Clinton warned her, as they walked across the sands to the car.