“But these friends of mine? These girls in the O Moo?” he protested.
“Oh! That!” exclaimed the sergeant. “What could you do? That was reported to the life-saving station hours ago. Best thing you can do is to help us track down the rascals who played such an inhuman trick on your friends.”
“What could have been their motive?” demanded Mark suddenly.
“That,” said the officer, “is a mystery which must be cleared up. We think we know. But you never can tell. Are you ready? We’ll have a cup of coffee before we go.”
A half hour later Mark found himself standing once more before the old scow. In the broad light of day it had lost much of its air of mystery. The door had been left open and had been blown half full of snow. Having climbed over this pile of snow, they entered the hallway and descended the narrow, circular stairs.
A hasty search told them that the place was deserted. A careful examination revealed the fact that the bottom of the scow had been cut away; that a cellar had been dug beneath it, then walled up with cement.
“Regular underground den,” the officer exclaimed. “Must have been a swarm of them.”
“Twenty or thirty, I guess,” said Mark absent-mindedly. He had picked up a clumsily hand-forged ax.
“Guess I’ll take that along,” he said presently.
In another room he found a large iron pot one-third full of a peculiar grease.