ng while the ghost was performing,"
Rick pointed out. "Only that no trace was left."

"You thinking about chemicals?" Scotty lengthened his stride toward the
inviting lights of the Miller farmhouse. "And speaking of same, I need
some for these mosquito bites."

"Chemicals can produce a mist," Rick pointed out, "without leaving a
visible trace. We didn't taste the water in the pool. I'm going to take
a sample tomorrow and see what I can find out."

The girls and the Millers were on the screened porch, waiting anxiously.

"No show," Rick called, anticipating the questions from the four on the
porch. "Not a sign of a spook. Only mosquitoes."

"I have something for those bites," Mrs. Miller replied quickly. "The
mosquitoes are fierce this year. Come into the kitchen and we'll treat
both of you."

Between applications of the aromatic ointment the boys reported on their
experience, or lack of it. Rick concluded, "So the ghost performs only
before an audience, and then only when notified in advance."

Dr. Miller smiled. "A pretty sweeping conclusion from a pretty small
sample, Rick. One experiment doesn't do more than give a single point on
the curve. You need more evidence than tonight's failure."

"We'll try again," Rick answered. He outlined the plan to let it be
known that they would be watching.

"That will be added evidence, but not conclusive," the scientist warned.
"But you're on the right track, I'd say. Now, let's leave ghosts and go
on to something more tangible. I have an interesting device made up of
alternate black and red squares, on which various carved pieces,
resembling royalty ..."

Rick held up a hand. "Say no more. I will be delighted to take you on
for a game of chess."

Barby and Jan returned to their own project, creating monograms to be
embroidered on their summer clothes, while Scotty and Mrs. Miller
settled down with books.

Rick knew from the start that he was no match for Dr. Miller, but he
resolved to give him as good a game as possible. An hour passed before
it was clear that Rick would be checkmated in two moves. He sighed.
"You've got me, sir. I guess ..."

The sentence was never completed. The quiet was abruptly shattered by
the strident blasting of the plane's alarm system!

Rick and Scotty were on their feet and running on the instant. Rick
reached the door first and threw it open, almost upsetting Belsely, the
tenant farmer.

The man's eyes were wide, and his face was pal