Chapter Page

1 The Earthquake                    1
2 The Mysterious Hitchhiker        11
3 Report from Interpol             18
4 Another Tremor!                  30
5 Secret Cache                     39
6 Brungarian Coup                  46
7 Wall of Water!                   55
8 A Suspect Talks                  65
9 The Cave Monster                 73
10 Energy from Planet X             83
11 An Electrical Christening        92
12 Exman Takes Orders               99
13 Disaster Strikes                106
14 Air-borne Hijackers             115
15 Kidnaped!                       125
16 A Unique Experiment             137
17 An Urgent Warning               145
18 Earthquake Island               155
19 A Fiendish Machine              166
20 The Robot Spy’s Story           177

CHAPTER I

THE EARTHQUAKE

“Tom, we’re having a problem with the gyro-stabilizer,” said Mark Faber, gray-haired president of the Faber Electronics Company.  “Hope you can find out what’s wrong.”

The eighteen-year-old inventor accepted the challenge with a smile.  “I’ll be glad to try, sir,” he replied.

Bud Barclay, a dark-haired young flier and Tom Swift Jr.’s closest friend, chuckled.  “If anyone can get the bugs out of your new invention, genius boy here will do it!”

The two boys followed Mr. Faber and his engineers to a wooden building which was tightly guarded.  Inside, a secret rocket-telemetering device was mounted on its test stand.

“As you know, Tom,” Mr. Faber began, “the usual conditions of rocket flight will be—­”

He broke off with a gasp of astonishment as the whole building suddenly began to shake.

“Good grief!” Bud exclaimed.  “This isn’t part of your testing routine, is it?”

His question was drowned out by cries of alarm and the sound of cracking glass.  The walls and roof were shuddering and creaking, and the concrete floor was heaving under their feet.

  [Illustration (earthquake in the lab)]

“Look out!  The test stand’s breaking loose!” Tom warned.

Mr. Faber and two of his men tried frantically to brace the heavy test stand which held the telemetering device.  Another engineer rushed toward the door to see what was happening outside.  Before he reached it, another shock knocked all of them off their feet.

Electronic equipment cascaded from the wall shelves, and a heavy-duty chain hoist came loose from its overhead track, plunging to the floor with a terrifying crash.

“An earthquake!” Tom gasped.

Bud, meanwhile, clawed a handhold on a wire screen enclosing an air compressor and pulled himself to his feet.  But the next moment a third, more violent tremor rocked the building, knocking him over.  “The roof!  It’s caving in!” he heard someone scream.