"I have found a weak link that breaks your whole chain," triumphed M. Paul. "The alleyway footprints are not identical with the soles of Kittredge's boots."
"But you said they were, the experts said they were."
"We were mistaken; they are almost identical, but not quite; in shape and size they are identical, in the number and placing of the nails in the heel they are identical, in the worn places they are identical, but when you compare them under the magnifying glass, this photograph of the footprints with this one of the boot soles, you see unmistakable differences in the scratches on separate nails in the heel, unmistakable differences."
Hauteville shrugged his shoulders. "That's cutting it pretty fine to compare microscopic scratches on the heads of small nails."
"Not at all. Don't we compare microscopic lines on criminals' thumbs? Besides, it's perfectly plain," insisted Coquenil, absorbed in his comparison. "I can count forty or fifty nail heads in the heel, and none of them correspond under the glass; those that should be alike are not alike. There are slight differences in size, in position, in wear; they are not the same set of nails; it's impossible. Look for yourself. Compare any two and you'll see that they were never in the same pair of boots!"
With an incredulous movement Hauteville took the glass, and in his turn studied the photographs. As he looked, his frown deepened.
"It seems true, it certainly seems true," he grumbled, "but—how do you account for it?"
Coquenil smiled in satisfied conviction. "Kittredge told you he had three pairs of boots; they were machine made and the same size; he says he kept them all going, so they were all worn approximately alike. We have the pair that he wore that night, and another pair found in his room, but the third pair is missing. It's the third pair of boots that made those alleyway footprints!"
"Then you think—" began the judge.
"I think we shall have found Martinez's murderer when we find the man who stole that third pair of boots."