“I know this stream,” said Pepper. “It is the Caboy River, and what you hear are the Falls. This is the place where that haunted mill is located.” CHAPTER XXIV WHAT HAPPENED UNDERGROUND “You mean the Robertson mill?” asked Andy. “Yes, the one mentioned by that Bert Field.” “Have you heard from that boy, Pepper?” “Not lately.” “Shall we go to the old mill and see what it looks like?” “We might pass it. We haven’t time to stop—not unless we want to get caught.” Still walking swiftly, the chums went along the river until they came in sight of the Falls. Not far off was the old mill. “Think we’ll meet that ghost?” asked Andy, as they paused at a distance to gaze at the ancient structure, some of the lower windows of which had been boarded over. “I don’t know I’m sure. Want to go closer?” “I’m not afraid.” “Come on then, and we’ll scatter some paper near the door. Maybe the crowd will think we entered the mill.” Knowing they had no time to spare, if they wanted to keep out of the reach of the hounds, the two cadets hurried on until they stood beneath a shed adjoining the old mill. “I don’t see anything unusual,” said Pepper, as he looked around. “Maybe this story about a ghost is all made up.” “Yes, but what about that yarn of a ghost that was half man, half beast?” “I don’t know. But I think——Hark!” Both boys listened. From inside the old mill a grating sound had reached their ears. “Why, I wonder if the wheel is going!” cried Andy. “It sounds like it.” “Let us look in at the door and see—if the door is unlocked,” was Pepper’s reply. The chums stepped closer to the doors of the mill. Scarcely had they done so when, without warning, some planking gave way and they found themselves dropping into some space below. Each tried to save himself, but it was too late, and down they went, into a lower apartment of the old mill. Then, as swiftly as it had moved before, the planking overhead closed, leaving the two cadets in almost total darkness. They were completely bewildered by what had occurred, and for the moment could do little but clutch each other and try to pierce the darkness which surrounded them. Andy had gone sprawling, with Pepper on top of him. Now both arose. “What do you make of this?” asked Pepper, trying vainly to control his voice. “I—I guess we have been trapped!” gasped Andy. “I—I wish we had a pistol, or something!” “Did we fall or was a trap-door opened, Andy?” “I guess a door was opened. Anyway, the opening is closed again.” “Well, I don’t believe any ghost did it, do you?” “No, it was some human being. But that human being might be just as bad as a ghost.” “Right you are. How are we going to get out?” “That remains to be seen.” The two boys felt around them. On every side was a stone wall. In two of the walls were doors. One was locked, but the other stood partly open.