"If your father knows all about this underground network of caverns and channels," Will said in a moment, "we'll have a happy old time finding him! He can dodge us here for a month."
"And those officers will have a fine old job getting the train robbers, too," Chester chuckled, "if they're acquainted with this underground system of highways. It strikes me," he went on, "that these train robbers have been here before."
"That may be!" answered Will. "In fact, it, occurs to me that your father searched out all these subterranean roads and rooms and showed them to the train robbers."
The boys proceeded downward for some distance and then stopped in a tolerably large chamber to rest and investigate.
"There's no use of our going on until we know whether the fellows you saw are coming in here," Will reasoned.
"I'm going up to the top again," said Chester, "and see what's going on there! The fellows I saw may be coming in."
Will waited for a long half hour for the boy's return, and when at last Chester slid down to him his face showed that he was frightened.
"They've got the combination to this channel all right!" he said.