"The returning footprints seem more distinct--better impressions."
"Yes; they are noticeably deeper. But there is something else." He produced a spring tape from his pocket, and took half a dozen measurements. "You see," he said, "the first set of footprints have a stride of twenty-one inches from heel to heel--a short stride; but he is a smallish man, and lame; the returning ones have a stride of only nineteen and a half inches; hence the returning footprints are deeper than the others, and the steps are shorter. What do you make of that?"
"It would suggest that he was carrying a burden when he returned," I replied.
"Yes; and a heavy one, to make that difference in the depth. I think I will get you to go and fetch Willett and the bicycles."
I strode off down the path to the entrance, and, taking possession of Thorndyke's machine, with its precious case of instruments, bade Willett follow with the other two.
When I returned, my colleague was standing with his hands behind him, gazing with intense preoccupation at the footprints. He looked up sharply as we approached, and called out to us to keep off the path if possible.
"Stay here with the machines, Willett," said he. "You and I, Jervis, must go and see where our friend went to when he left the path, and what was the burden that he picked up."
We struck off into the wood, where last year's dead leaves made the footprints almost indistinguishable, and followed the faint double track for a long distance between the dense clumps of bushes. Suddenly my eye caught, beside the double trail, a third row of tracks, smaller in size and closer together. Thorndyke had seen them, too, and already his measuring-tape was in his hand.
"Eleven and a half inches to the stride," said he. "That will be the boy, Jervis. But the light is getting weak. We must press on quickly, or we shall lose it."
Some fifty yards farther on, the man's tracks ceased abruptly, but the small ones continued alone; and we followed them as rapidly as we could in the fading light.
"There can be no reasonable doubt that these are the child's tracks," said Thorndyke; "but I should like to find a definite footprint to make the identification absolutely certain."
A few seconds later he halted with an exclamation, and stooped on one knee. A little heap of fresh earth from the surface-burrow of a mole had been thrown up over the dead leaves; and fairly planted on it was the clean and sharp impression of a diminutive foot, with a rubber heel showing a central star. Thorndyke drew from his pocket a tiny shoe, and pressed it on the soft earth beside the footprint; and when he raised it the second impression was identical with the first.