n
appeared, carrying a fifth. The door shut behind them and they made
their way slowly toward the waiting globe. They laid down their burden
and one of them turned a flash-light on the globe and opened a door in
its side through which they hoisted their burden. They all entered the
globe, the door closed and with a slight whirring sound it rose in the
air and moved rapidly toward the northeast.

"That's the place we're looking for," muttered Dr. Bird. "We'll go
around this hollow and look for it. Be careful where you step; they
must have ventilation somewhere if their laboratory is underground."

Followed by the secret service operative, the doctor made his way
along the edge of the hollow. They did not dare to show a light and it
was slow work feeling their way forward, inch by inch. When they had
reached a point above where the doctor thought the light had been he
paused.

"There must be a ventilation shaft somewhere around here," he
whispered, his mouth not an inch from Carnes' ear, "and we've got to
find it. It would never do to try the door; if any of them are still
here it is sure to be guarded. You go up the hill for five yards and
I'll go down. Quarter back and forth on a two hundred yard front and
work carefully. Don't fall in, whatever you do. We'll return to this
point every time we pass it and report."

The operative nodded and walked a few yards up the hill and made his
way slowly forward. He went a hundred yards as nearly as he could
judge and then stepped five yards further up the hill and made his way
back. As he passed the starting point he approached and Dr. Bird's
figure rose up.

"Any luck?" he whispered.

Dr. Bird shook his head.

"Well try further," he said. "I think it is probably beyond us, so
suppose you go fifteen yards up and quarter the same as before."

* * * * *

Carnes nodded and stole silently away. Fifteen yards up the hill he
went and then paused. He stood on the crest of the hill and before him
was a steep, almost precipitous slope. He made his way along the edge
for a few yards and then paused. Faintly he could detect a murmur of
voices. Inch by inch he crept forward, going over the ground under
foot. He paused and listened intently and decided that the sound must
come from the slope beneath him. A glance at his watch told him that
he had spent ten minutes on this trip and he made his way back to the
meeting place.

Dr. Bird was waiting for