“That might work,” Pyros said thoughtfully. “It can sense heat from a long way off. But if you hurt it, it will flee through the rock. You will need to trap it somehow.”

“I think I can manage that,” Alice said. “We should start as soon as we can, before it comes back here.”

“I agree. I will have material for the fire fetched.” Pyros got to his feet. “You will need a guide. If you do not object, I will assign Flicker.”

“Him?” Alice frowned. “He seems to hate me.”

“He needs to learn to work with Readers, whatever his feelings,” Pyros said. “And he owes me a penance for disobedience. You will find he is quite a clever boy, when he wants to be, and he has explored farther than anyone else.” The old man hesitated. “Just . . . make sure that he is careful.”

“I’ll do my best,” Alice said.

As they walked through the endless, meandering tunnels, Flicker told Alice, grudgingly, about his world. The boy seemed caught between his dislike of her and pride in his knowledge, and eventually he couldn’t resisting showing off.

“At the bottom of the world is the Heartfire, where the rock is so hot, it glows and runs like water. All these tunnels”—he waved a hand at the winding corridor they were walking through—“were formed by the Heartfire in the old days. They wind around and on top of each other, like a bucket of worms, all the way up to the surface.”

“What’s on the surface?” Alice said. She was fascinated. While she’d explored through quite a number of portal-books in her errands for Geryon, this was the first time she’d felt a real sense of being on another world.

“Nothing,” Flicker said. “It’s just cold and dark. I’ve been up there,” he added with a touch of pride. “Nobody else from the village has done that.”

“Is that where the bluechill comes from?”

Flicker nodded. “The wild gate is up there, somewhere. The bluechill comes from the other side. We used to live there, until—” He glanced at Alice, stopped, and shook his head sharply.

“Until what?”

“Never mind,” Flicker said abruptly. “This is what we’re looking for.” He pointed ahead, where the corridor flared outward into a wider, taller space.

Alice held her glowing hand high to augment the light from Flicker’s hair. The same lava that had made the tunnels had also created a natural amphitheater, a large, roughly circular room, dished at the bottom. Or perhaps not entirely natural—there were at least three doorways leading off into other passages that looked like they’d been shaped by intelligent hands.

“Did your people used to live here?” Alice said.

“When the Heartfire was warmer, and there were more of us,” Flicker said, and scowled. “That was a long time ago.”