To reach the Tunnel Tree, they had to walk around a sloping path, up past a hilly meadow, and along the edge of a ridge. It was silent in the forest, except for the rustling of leaves and the scurrying of squirrels, and their footsteps sounded loud on the dry, leaf-strewn ground. Neil had brought along the flashlight from the pickup, but the woods were still dark and shadowy under the cloudy sky.

Halfway along the ridge, they came to an enormous fallen redwood, fenced off with chain link. Neil shined his torch on it, and the wood glistened and sparkled. Like all the petrified trees in the forest, it had been infiltrated with silicas from volcanic lava, which had turned it gradually into stone. The massive trunk, over four feet across and hundreds of feet long, disappeared into the rocky hillside, and beside it ran a narrow tunnel cut into the limestone and shored up with planks.

From within the tunnel, they could see lights.

“Okay,” said Harry. “I think I’d better lead the way.”

They entered the tunnel, heads bent, and walked along the boarded floor until they reached the end. There, sitting on a campstool in front of the petrified tree, with a battery of flashlights and cameras and drawing equipment, was a middle-aged man in jeans and a lumberjack shirt, peering closely at the bark through magnifying spectacles.

Harry stood beside him and waited. But the professor was so engrossed in what he was doing that he stayed where he was, his head bent, his heavy eyebrows drawn together like aggressive caterpillars, his hairy hand poised to draw a line of India ink on his drawing pad.

It was clammy and warm in the tunnel, and Harry tugged at his collar.

“Excuse me,” he said. “Are you Professor Thoren?”

The professor’s body flinched. Then, very slowly, he sat back on his campstool and turned toward them. His eyes were so grossly enlarged by his magnifying lenses that Harry felt a ridiculous momentary shock. But the professor took the glasses off, and replaced them with a pair of normal eyeglasses.

“Do you have any idea of the concentration it takes to make sense of these hieroglyphs?” he said, in a deep, New England accent.

Harry grinned and shrugged, and the professor sighed, “No, you obviously wouldn’t. But your interruption, let me assure you, has cost me two hours’ train of thought.”

Singing Rock said, “We wouldn’t have interrupted you at all, professor, but it’s desperately urgent. Many lives are at stake.”

“Urgent?” queried Professor Thoren. “How can anything to do with these hieroglyphs be urgent? They’ve been here for two thousand years, or even longer. This tree has lain here for six million years. In this sort of business, nothing is ever urgent. How can it be?”