As they entered they could hear a confused uproar ahead. The roar of an automobile, the sound magnified tenfold in the subterranean passages, crashed out. There were shouts, cries of warning and alarm.
"We've got them trapped!" shouted the trooper.
They stumbled down the rocky passage. A man came blundering around a corner, right into the arms of the foremost officer. He was seized, there was a gleam of metal, a click, and the auto thief was handcuffed before he fully realized what had happened.
"One!" counted the sergeant. "Now for the others!"
They passed the Hardy boys' roadster and caught a glimpse of a man fleeing before them into the main cave. The trooper drew his revolver and sent a shot over the fellow's head.
The man came to an abrupt stop and raised his arms. He surrendered without a fight.
"Two!" yelled the sergeant gleefully, pouncing on his prisoner. Another pair of handcuffs was produced, the chain was slipped through the chain of the other thief's shackles, and the pair were swiftly manacled together.
The officers plunged on into the main cave.
In the glare of the flashlights they saw the truck and one of the pleasure cars standing by the wall. The two other cars that had been in the cave had disappeared. No men were in sight.
The raiding party heard the roar of a racing engine, a grinding of brakes, and a confusion of shouts.