Shinji and Roux pushed. For a moment, nothing happened. It felt to Shinji like they were pushing against the side of a mountain. But then something gave way, and the door made a grinding, groaning sound as it swung slowly back. Through the doorway, a narrow stone tunnel wound its way into the darkness.

Lucy clucked her tongue. “Huh. First time for everything, I suppose.”

Shinji stared into the passageway. He could feel something deep within the mountain and knew that once he stepped through the door, there was no turning back. Lucy and Roux stood beside him; could he really ask them to follow him down into the unknown?

“Come on,” Roux said, as if reading his thoughts. “Are we doing this or not?”

“Yes,” Lucy added. “We’ve come this far and opened the door. Might as well keep going. Tinker…” She raised her hand, and the mechanical mouse hopped into it. “Illuminate,” she whispered, and Tinker’s eyes flashed as two thin yet oddly powerful beams of white light emerged from them, shining into the dark passage. Lucy raised her arm, and the mechanical mouse leaped off her hand onto Shinji’s shoulder, weighing almost nothing as he crouched there, shining his light into the darkness of the tunnel.

“Let’s go,” Lucy told Shinji, gesturing down the passageway. “We’ll follow you.”

Shinji nodded and took a deep breath. With Tinker’s light showing the way, they stepped through the door into the side of the volcano.

The passage didn’t go very far. Shinji and the others had only taken a few dozen steps into the tunnel before it ended in a long stone stairwell, descending into the darkness. Torches jutted out of brackets on either side of the tunnel, flames flickering brightly. No one asked how that was possible; the force in the mountain was obviously waiting for them. Without hesitation, Shinji and the others started downward, heading deeper into the volcano.

At first, the atmosphere in the stairwell was damp and cool. However, the farther they went, the hotter the air became. Shinji was sweating again, moisture trickling down his forehead and running into his eyes, making them sting.

Finally they reached the bottom of the stairs, where another short stone passageway continued into the mountain.

“Man, it’s like an oven in here,” Roux said, wiping his brow as they walked down the tunnel, Tinker’s eye beams lighting the way. “And what is that smell?” He waved a hand in front of his nose. “Ugh, that’s nasty. Who had too many beans for lunch?”

“It’s sulfur,” Lucy told him, wrinkling her nose. “So don’t even look at me. I wonder how close we are to the actual lava.”

The tunnel ended, opening up into an enormous cavern. Large cracks snaked along the floor, venting steam into the air. Spikes hung from the ceiling, not made of stone, but shiny, black, and wickedly pointed, like obsidian. They reminded Shinji of huge shark teeth, dangling ominously overhead.

“Ugh, I feel like we’re in a mouth,” Lucy muttered.

“A mouth that really needs toothpaste,” Shinji added.

Roux snickered. “And a breath mint—”

There was a crunch that seemed to echo through the chamber, and Roux’s foot disappeared as a portion of floor crumbled beneath him. Roux yelled and flailed his arms, trying to keep his balance as more cracks appeared in the rocks at his feet, revealing an ominous red glow beneath. He teetered a moment, then started to fall.

Lucy lunged, grabbed Roux’s wrist, and yanked him forward just as the stones he’d been standing on crumbled

and dropped into the bubbling pool under the surface of the rocks. Panting, Lucy and Roux swiftly backed away from the hole, joining Shinji, who let out a sigh of relief.

“That was close!” Lucy gasped as Roux leaned against a rock and slid down into a sitting position. His face pale, he stared at the hole he’d almost fallen into, as if just realizing how close he’d come to a very painful death.

“Are you guys all right?” Shinji asked.

Roux nodded, wiping sweat from his eyes. “I haven’t had a bath in a month,” he muttered. “I do not want my first one to be in lava.” He glanced at Lucy, giving her a wry smile. “You have good reflexes for a rich tourist girl,” he said almost begrudgingly. “I would’ve expected you to let me fall.”

Shinji crossed his arms. “You have a weird way of saying ‘Thanks for not letting me fall into lava and melt to death.’ ”

“Sorry.” Roux held up both hands. “I didn’t mean it like that. It’s just…I don’t know anyone else who would’ve bothered to help me.” He shrugged, glancing at Lucy. “So, uh…thanks. For not letting me fall into lava and melt to death.”

“It’s fine.” Lucy waved him off, though she gave Shinji a quick smile. “Don’t worry about it. When you’re a member of the Society of Explorers and Adventurers, you have to be ready for anything. Sharks, snake warriors, rickety bridges over ravines…” She glanced at Shinji with a wry grimace. “You’re not the first person I’ve saved from falling to their death while on a mission for SEA.”

Shinji held out a hand and pulled Roux to his feet while Lucy gazed around the cavern. “This must be a lava tube or something,” she mused, watching steam writhe out of a crevice and coil up toward the ceiling. Glancing at the ground, she gently tapped the rocks with the toe of her boot. “I bet the whole floor beneath us is magma.”

“Oh, that’s great,” Roux said, staring at the other side of the cave, which now felt like a million miles away. “So, how do we get across?”

“Very carefully.” Lucy grimaced. “As Scarlett would say, ‘No one think heavy thoughts.’ ”

With the utmost care, they tiptoed across the cavern. Shinji found himself holding his breath every time he put his foot down, ready to freeze or leap back should the floor crumble under his shoes. Sometimes, he could hear the lava, slowly churning and bubbling right below them, and sweat ran down his face from more than the heat.

After what felt like hours but was really only a few minutes, they reached the other side of the cavern. The ominous burbling of lava under their shoes faded, and the temperature got a little cooler. Once they were in yet another tunnel, Shinji took a deep breath of not-quite-stifling air, though it still felt like he was breathing through a hair dryer.