During the time that Billings was making his preparations for the last act of his life, Sam and Fred remained seated a short distance from the cut which led to Skip's hiding place.
Both were listening intently for the first sound which should betoken the coming of the miners, and the falling earth which was displaced by Billings' feet as he worked in the cutting attracted their attention.
"There's some one in the tunnel we made," Sam whispered. "Let's creep up and find out who it is."
"That won't do, for there's no chance Billings would come back if he once got out, and we should arouse suspicions."
Despite this warning Sam advanced a short distance, and on becoming convinced that the tunnel really had an occupant rejoined Fred, as he whispered:
"We'd better sneak further along. I reckon somebody is on guard up there, and we musn't be seen so far down."
He had held the shovel during this excursion, and still retained it as they walked noiselessly along the drift until arriving at the mouth of the short slope.
Here the two halted at the moment when the confined gas, ignited by the open lamp, burst its bonds, and the shock sent them headlong up the incline.
Huge masses of earth were detached on every hand, except directly in the narrow way leading to Skip's hiding place, and on scrambling to their feet a solid wall shut them out from the drift.
"What was that?" Fred cried in alarm, as he assured himself his lamp was uninjured.