w his way around."

Jan Miller pointed out, "But he floated right over the quarry and you
fell in."

"It wasn't like that," Scotty corrected. "We stopped because the ghost
had vanished. It's not hard to see why. He switched off the light,
walked around the edge of the quarry, then switched on again."

"That has to be it," Rick agreed. "Now, why try to lead us on like that?
It was only an accident that Scotty and I didn't go in together, because
his shoe needed tying. Otherwise, we'd both have been at the bottom of
the quarry."

Dr. Miller shook his head, in bewilderment, not in negation. "You might
very well have been hurt seriously or even killed. In which case people
would have blamed the ghost. But why did the ghost do such a thing?"

Rick had wondered about this, too. "I can think of only one reason. The
ghost can't stand investigation. He knew we were a menace because Scotty
and I ran right up and tried to catch him that first night."

"But why did he tamper with your plane, or try to?" the scientist asked.
"He couldn't have known about the alarm. You checked the plane, didn't
you?"

"Yes. It wasn't touched, so far as we could see. Anyway, no harm was
done. I can't imagine why he went for the plane, though, unless he
figured on sabotaging us that way."

"You still haven't told us why you suspect the Frostola man," Barby
pointed out.

Rick ticked off the points on his fingers. "He's new. He arrived just as
the ghost started making appearances. But he's not so new that he hasn't
had time to study the area or to make plans to lead nosy people to the
quarry. He was at the picnic ground when there was no chance of selling
much ice cream. He took the cement bags; we don't know why. He's tall
and lean, so he could run fast enough to keep ahead of Scotty and me.
He's also tall enough to qualify for the ghost we chased."

He stopped and took a deep breath. "And one more thing. He carries
something that would make a marvelous mist for a ghost to appear in.
Something that might harm the microscopic animals in the pool
temporarily--although I'm not sure of this--but would be gone with the
mist."

The others stared at him with complete interest.

Dr. Miller said softly, "Of course! Rick, that's brilliant. It fits
perfectly!"

Jan Miller wailed, "What does?"

"Dry ice," Rick said.

CHAPTER IX

The Splitting Atoms

The storm had given way to a fine drizzle of rain by morning. Rick
stared out the wi