"I hardly know what to think. I have an idea, however, as to where the charge was dropped from."
"From where was it dropped?" demanded the superintendent sharply.
"From the first sub-level below the surface. You see, it would be very easy for anyone to go down that ladder there at night, without attracting attention. He could have dropped the charge down through the shaft and been out and away long before you telephoned up here."
"That is very true. It may explain that part of the affair."
"We found a fuse on the first sub-level near the shaft, but of course that doesn't prove anything. It may have been dropped there by any one of fifty different men."
The superintendent's face was stern as he pondered over the matter that was disturbing them all.
"Rush, I want you boys to devote your time, during the next few days, to working on this case. I know of no one else better qualified to do it. If you can't get to the bottom of the mystery, I know of no one who can. In the meantime I shall be pursuing some investigations of my own."
"Very well, sir; do you wish us to drop our work?"