"What's up now?" demanded Chester.

"I don't know; but that explosion sounded to me as if there were
something wrong ahead. I wouldn't be surprised if the Germans had
dynamited the bridge."

"By George! I believe you are right," exclaimed Chester. "I wouldn't have
thought of it, and if I had been in your place at the throttle the
chances are we would have gone over if such is the case."

"Well," said Hal, "I'll climb down, take a walk ahead and investigate."

"I'll go with you," declared Chester.

"No, you won't. You stay here and watch the engine."

"You are right, as usual," said Chester. "But don't be any longer than
you can help."

Hal agreed, and a moment later Chester lost sight of him in the darkness.

Slowly and cautiously Hal made his way along the track. As he moved
stealthily around a curve in the road the cause of the explosion became
apparent. It was even as he had feared. His quick wit had detected the
meaning of the explosion and none too soon.

Just ahead, where a short time before had been a bridge spanning a deep
chasm, there was now nothing but space. The bridge had been blown up. Had
Hal applied the brakes to the engine one minute later, in spite of the