"And that light," continued Tom, pointing down the length of the tunnel. "Do you suppose it's Miles and Brett?"
"It isn't moving," commented Astro.
"Well, since we're here we might as well find out as much as we can," Tom decided. "Let's go."
The two cadets flattened themselves against the side of the shaft and inched forward. The hissing noise was slowly building up to a roar now, and as they made their way along the shaft, they passed other smaller tunnels that branched off to the left and right. There was evidence of recent work. Tools were scattered along the tunnel floors, as if the workers had dropped them in sudden flight.
The light ahead of them grew brighter, and as they rounded a corner, they saw a bare, unshaded lamp suspended from the roof of the tunnel.
Tom suddenly stopped and jerked Astro back. "Look!" he exclaimed, pointing to the floor, not two paces away. A thin wire, hardly noticeable, was stretched across the floor at ankle height.
"That bright light is to attract your attention while you trip over that thing and probably blow yourself to bits," he said grimly, pointing to the wall where the wire was connected to a small charge of explosives. "Nothing to bring the roof down," he continued, "but enough to blast whoever tripped over this wire."
Stepping over the wire carefully, they started down the shaft again, but Tom paused thoughtfully.
"What's the matter?" asked Astro.
"That booby trap," said Tom. "We'd better not take any chances of tripping over it on the way back. We might be in a hurry."