The men had no sooner begun to look around the huge underground chamber when a fearsome growl rumbled through the cave.  Everyone whirled about and the next instant froze in horror.

A huge bear reared up in the mouth of the cave!  The monster snarled and blinked its yellow eyes in the glare of lights.

“We’re trapped!” Hank cried out.

The enormous bruin was now waving his huge head from side to side, as if daring the intruders to step up and fight.

Several of the government men had brought rifles and shotguns.  But in spite of their peril, no one wanted to shoot the handsome old fellow.

“I’ll send out an SOS,” Tom said.  “If help arrives before the bear attacks, we won’t use guns.”

He radioed the local Forest Ranger post.  After a nerve-racking wait, with the group expecting a charge from the beast at any minute, two rangers appeared and captured the bear with a net.  One man of the government work crew knocked together a stout wooden cage.  The beast, outraged, was loaded aboard the heliplane to be released in an area remote from the cave.

  [Illustration (Tom and Hank meet a bear in the cave)]

Now the grueling job of installing the Quakelizor began.  First the cave was cleared of debris, bats, and other small living creatures.  Then a site was marked out on the cave floor.  Tom had brought along a midget model of his great atomic earth blaster, which he had invented to drill for iron at the South Pole.

With the blaster, Tom quickly drilled a pit of exact size into the bedrock.  Then the Quakelizor was assembled and lowered into place by a portable crane.  A power plant and radio antenna were set up and the installation was finally completed.

“I must return to Shopton now,” Tom said.  “Art here will stick around and help you operate the setup,” he told the government engineers after radio contact had been made with Washington.  “If anything goes wrong, just flash word to Enterprises.”

The Sky Queen and the heliplane sped back across the continent.  As Tom landed at Enterprises he was greeted by Bud, who came speeding out on the airfield by jeep.

“Just got back from the space wheel about an hour ago,” Bud said.  “Your dad’s really worried about those exploding radio sets, Tom.  He has no clues, but he’s sure the scientists working for the Brungarian rebel setup are responsible.  He thinks they may try to ruin all of Enterprises’ communications system by remote control.”

Tom’s face was grave as he listened.  The two boys discussed the problem as they drove to the Swifts’ office in the main building.

“Boy, I sure wish I could think of some way to cope with it,” Tom said wearily, flopping down in his desk chair.

“Your dad said to give it the old college try,” Bud reported.  “And he also said he’d be back in two days to help you on the problem.”

Tom glanced at the calendar.  “Which reminds me,” he said, “on Monday the brain energy will be due from space!”