" Barby said flatly.

"Maybe," Rick said. He didn't know why he was still skeptical. The
apparition had been really blood-curdling in its apparent realness, but
he still wasn't ready to buy a supernatural explanation.

Jan Miller replied with an appropriate quote from William Shakespeare.
"There are more things in heaven and on earth than are dreamed of in thy
philosophy, Horatio Brant!"

Rick grinned. "That's true. No one knows better than I how ignorant I
am. I can only say that I'm trying to learn. Let's climb down and look
at the pool."

He led the way down the rocky slope to where the rusted iron pipe jutted
from the side of the Hill, a thin trickle of water dripping constantly
into the pool below. The pool was actually a catch basin in the rock.

Rick examined the pipe. It was ordinary, rusted but still sound. It held
no secrets that he could see. He held his mouth under it and tasted the
water. It was cold and good, typical spring water, with the taste of
minerals in it. He knew from Dr. Miller that it was good to drink.
Picnickers used it regularly.

"Expect evidence to float out with the water?" Barby asked.

"Never can tell," Rick said, unperturbed. His sister, even more than Jan
Miller, was an incurable romantic. If the ghost turned out to be
something other than the pitiful shade of Captain Costin, she would be
bitterly disappointed, Rick knew.

He got down on his knees, Scotty beside him, and they probed in the
water of the rocky basin with their hands. There was a layer of brown
algae in the bottom, which was to be expected. It looked dead, but when
Rick scraped it, there was green underneath the brown.

Scotty took out his jackknife and probed with the largest blade.
Clearly, there was nothing in the basin but a solid rock bottom.

The boys' eyes met. "The pool bubbled a little last night," Rick
recalled.

Scotty nodded. "I saw it, too. But there's nothing there to make it
bubble."

Jan Miller shuddered. "I almost died when you two idiots scrambled up
here. You went right into that awful mist!"

Rick remembered the icy tendril that had curled around his face and a
little chill went through him. "It was cool," he said. "At least the
Blue Ghost isn't warm. Maybe he's blue with cold."

Scotty used his jackknife to probe at cracks in the rocky hillside. It
was seamed with them, but he found nothing unusual. "I give up," the
dark-haired boy said, his face showing his bewilderment. "There's
ab