A gust of hot wind blew against Samantha’s matted hair. They stopped descending and started moving sideways through the cavern as a new stream of air caught them. The balloon lurched, and the bucket shook.

They moved faster now. Samantha guessed they were sailing at least twenty miles per hour.

Her ears popped. The cavern walls parted, and they entered a vast open space. It made the slidewalk hangar in Seattle seem tiny.

And the space was hot. So hot that Samantha started to sweat.

A deep, low rumble filled the air, and everything around them lit up in the bright orange light.

It was getting even hotter!

Her weight shifted and the bucket wobbled. She straightened up quickly.

“Careful, Sam,” said Nipper. “I don’t want to get dumped out here.”

He tilted his head to gesture at the cavern floor below.

She looked down.

Sharp limestone spikes pointed up. She and her brother drifted above a field of stalagmites. The light came from glowing orange rivers of lava, splashing and rumbling across the rocky floor. Plumes of sulfurous steam rose from bubbling craters filled with molten rock.

Samantha wiped sweat from her forehead and looked up.

The balloon coasted below a field of sharp stalactites. Slivers of light came through cracks in the stone above, joining reflected orange light from the lava below.

It finally dawned on Samantha: they were inside a volcano!

Samantha wanted to try on her glasses and look around, just in case there was a PSST or a clue, but it seemed wiser to stay still.

“Watch out!” Nipper shouted.

A black shape moved toward them from the side. It swerved and zoomed, squeaking and fluttering away.

“Don’t worry,” Samantha said. “It’s just a bat. It won’t bother us.”

“No, Sam,” Nipper said, waving urgently. “Look where we’re going.”

Ahead of them, the cavern ended. A wall of sharp rock pointed at them like needles. Samantha squinted and saw an oddly shaped opening in the wall. It was wide and round at the top, then narrow at the bottom. The shape reminded her of a soft-serve ice cream cone. They were coming up on it, fast!

“Hands inside the bucket,” she said to Nipper, and prepared for impact.

They fit through the hole—just barely. The balloon carried them into a new room and landed gently on a flat surface. They waited, staying still in the center of the bucket.

“Sca-ree,” said Samantha.

Nipper nodded. After another minute, he hopped out of the bucket and onto the floor.

Samantha felt the bucket rising again and she got out, too. As soon as her feet were on the floor, the balloon and bucket floated up and away.

Bang!

The sound made Samantha jump. Somewhere overhead, a stalactite had popped the balloon.

The wooden bucket crashed to the floor a few yards from them.

It was colder in this new area, and quieter. Samantha heard the familiar swishing-sandpaper noise.

“Slidewalks,” she said.

They stood in the center of a smooth concrete slab. It was about the size of a tennis court, but square and without a net. A set of twenty slidewalks moved to and from each side of the square. The belts disappeared into tunnels labeled with glowing signs similar to the ones under Volunteer Park.

AUSTRALIA

2,100 MILES

CHINA

3,700 MILES

INDIA

4,000 MILES

UNITED STATES

8,300 MILES

“Where to?” Nipper asked.

Samantha glanced down at her left foot. There was a hole in her sock. She looked at her brother. Brown sludge caked his body from head to toe. Her shoulder stung from the circus peanut. She was exhausted, and they had zero clues.

“Home,” she said. “We’ll start again tomorrow.”

Samantha was about to step onto the slowest U.S.-bound slidewalk when she noticed something in the distance.

“Wait,” she said, and walked over to investigate. “Come see this.”

Just past the edge of the concrete slab, a slender stalagmite, about two feet high, stuck out between some rocks. A plastic crate rested beside it. Samantha bent down and lifted something from the crate. It was a deflated inflatable animal. She stretched it out on the floor. It had a black-and-white-striped tail and a black mask across its eyes.

“That’s kind of neat,” said Nipper, studying the stalagmite. “Do you think it does something super-secret?”

“Not that,” said Samantha. She pointed at the deflated animal. “This.”

“A raccoon,” said Nipper.

“It figures,” said Samantha. “Morgan Bogan was telling the truth…and Uncle Paul was here.”

Nipper looked confused.

“It was all in that note from opening day,” Samantha said. “I think this raccoon is meant to let us know that Uncle Paul was here.”

Nipper shook his head.

“Beats me,” he said. “But I’ll take your word for it.”

Samantha frowned. How could anyone remember 783 varieties of candy, the name of the waffle iron inventor, and that Mali is one of sixteen landlocked countries in Africa, but not recall important details that could help them find their missing uncle?

“You are a master of useless facts,” she said, irritated.

“Thank you,” Nipper replied.

Samantha hadn’t meant it as a compliment, but she gave up on the conversation.

She took another look inside the crate and saw three sheets of scratch-and-sniff stickers—the ones she had given Uncle Paul months ago. She ran her hand along the top page, being careful not to scratch. Near the bottom, the strawberry sticker was missing, of course. Uncle Paul had placed it on the letter he left for her in Edfu, Egypt. She felt the empty outline of the berry and looked next to it at the sticker of a tomato.

“I know what you’re thinking,” said Nipper.

“What?” she asked.

“You’re wondering if a tomato is a fruit or a vegetable,” he replied. “Fruit.”

He flashed a smile.

Samantha scowled.

“So’s a chili pepper,” he added. “Did you know that the Scoville scale is how scientists measure—”

“A pepper is most definitely not a fruit,” said Samantha.

She flipped through the three pages of stickers. On the third sheet, between a banana and a cranberry, she saw a chili pepper.

Nipper crossed his arms and flashed her another big smile.

“I’ve had it with you!” she shouted, and stood up.

She felt her right toe poke through the hole in her sock.

“You know every kind of stupid fruit there is, but you’re too stupid to NOT press the stupid button on a stupid rocket before I’m strapped in!”

Nipper stopped smiling.

“I’m going home,” she said, rolling up the sticker sheets and stuffing them into her pocket.

She stepped onto the slowest-moving conveyor belt.

“I’ll see you in Seattle,” she said. “If you can manage to get there without doing something incredibly dumb.”

Samantha stepped quickly to the farthest, fastest Seattle slidewalk. She caught her balance and watched Nipper recede into the distance.

Then she stomped on a bubble and zoomed away.