I looked out too, to see what was interesting him. Directly below us lay the encampment of the workmen whom I had seen in the morning. They had hewed up a few yards of the wood pavement, and the smaller of the two men was now immersed up to his waist in a hole, working rather laboriously in the restricted space at his command with a pick-axe. The boy was piling wooden blocks into a neat heap, and the big man, whose form was only partially visible, was doing something inside the wigwam. The roadway was more than half blocked, and cabs and omnibuses, in charge of overheated and eloquent drivers, were being filtered through the narrow space left at their disposal by a phlegmatic policeman. "Look here," said Champion. I looked. "What on _earth_ are those fellows doing?" he continued. "Re-laying the road, perhaps." "One doesn't re-lay a road by making a deep hole in it." "Well--gas!" "Gas and electric light mains in this street are all led along a special conduit reached by manholes every eighty yards," said Champion. "There's no need to dig." "Well--drains!" said I vaguely. But I was a mere child in the hands of this expert. "The drains, as you call them," he said testily, "consist of a great sewer away in the depths, accessible from various appointed places. Besides, nobody in his senses tries to lift earth out of a hole with a pick-axe." "Perhaps the solution of the mystery lies inside the wigwam," I said. "No. That is just what complicates matters. When a shaft leading down to the electric light mains is opened, one of those canvas shelters is put over the top. Now there is nothing under that shelter--nothing but the bit of road it covers. The thing seems to be simply a stage accessory, planted there to give the encampment an aspect of reality. Ah, look at that!" "That" was a small piece of paving-wood, dexterously hurled by the dirty-faced boy, who seemed to be finding time hang rather heavily on his hands. It took a passing citizen in the small of the back, but when he swung round to detect the source of the missile the boy was on his knees again industriously blowing up the brazier. With an indignant snort the citizen passed on his way, doubtless adding the outrage, in his mind, to the long list of unsolved London crimes. But retribution awaited the youthful miscreant. The phlegmatic policeman who was regulating the traffic on the single-line system happened to notice the deed. He walked majestically across from the far side of the street towards our excavating friends. "Come on!" said Champion to me. "There's going to be some fun." We stepped out through one of the windows, which possessed a broad balcony, and took our stand behind some laurels in tubs which lined the balustrade. The street was comparatively quiet at the time, and we were able to hear most of the dialogue that ensued.