ter another, on the lighted
oscilloscope screen mounted above the keyboard.

Tom and his father read the tape as it unreeled.

SPACE BEINGS TO SWIFTS. REQUEST INFORMATION ON PROGRESS AND
RESULTS OF ENERGY SENT TO YOUR PLANET.

After a quick consultation with his father, Tom beamed out the reply:

WE ARE PLEASED WITH RESULTS SO FAR. FURTHER EXPERIMENTS NOW
GOING ON. REQUEST VISIT TO CONTINUE LONGER THAN TWENTY-ONE DAYS
AS PLANNED.

Hopefully the Swifts stood by the machine. Would their space friends
agree? As the minutes went by without a response coming through, father
and son exchanged anxious glances.

"They've _got_ to let Exman stay, Dad!" Tom said.

Mr. Swift nodded. "I'm afraid, though, the space beings have decided
otherwise. They--"

He was interrupted by the ringing of the alarm bell. "Message, Dad!" Tom
said tersely.

A moment later they were overjoyed to see three words appear on the
tape:

VISIT EXTENSION GRANTED.

Relieved, the two scientists went back to work on their sensing
experiments. Twenty minutes later the signal bell rang again on the
electronic brain.

"This time it _must_ be Exman!" Tom cried.

The unreeling tape quickly bore out his guess.

EXMAN TO SWIFTS. TWENTY-FOUR-HOUR EARTHQUAKE UNDER HIGH LOYALTY.

"What!" Tom stared at the tape, his brow creased in a puzzled frown.
"That 'twenty-four-hour earthquake' bit must mean he's warning us that a
quake will occur in twenty-four hours. But what about the rest of it?"

"Hmm... 'Under high loyalty.'" Mr. Swift was as baffled as Tom. He
studied the message for several minutes. It seemed highly unlikely that
the electronic brain had made an error in decoding. Any new or
untranslatable symbol caused a red light to flash on the machine.

"I think the only thing we can do is signal Exman and ask for a
clarification, Tom," Mr. Swift decided at last.

Tom agreed. He beamed out a hasty code signal:

EXPLAIN MESSAGE.

Seconds later came Exman's reply. It was identical with the first
message:

TWENTY-FOUR-HOUR EARTHQUAKE UNDER HIGH LOYALTY.

Tom and Mr. Swift stared at each other anxiously.

"Good night, Dad! This is horrible!" Tom exclaimed. "Exman sends us
ample warning of a disaster and we're stymied!"

[Illustration (Tom Jr. and Tom Sr. read a message from Exman)]

"Hi! What's going on, you two?" asked a merry voice. "More heavy
thinking?"

Sandy Swift stood smiling in the doorway. Th