Simber crouched on the rocks nearby. He ignored the others and stared to the west, sampling the air now and then.

It was a long day with little activity on the upper level. Just the occasional man or woman in dark trousers and bright-colored or white flouncy shirts. Some of the shirts were adorned with gold bars or symbols, and others were plain. Some of the men and women sported tattoos and scars, making them look quite dangerous.

Now and then they saw women in elegant dresses, complete with petticoats and feathered hats that would make Mr. Appleblossom sigh in delight. But there was no sign of Copper in her dingy brown slave clothing.

At nightfall, Simber carried Crow to the ship so he could sleep, but Sky refused to go, so Carina and Alex stayed with her. Their muscles ached from crouching all day.

It was actually easier to see into the reverse aquarium in the dark. And now they could lean over the skylight without fear of casting a shadow and being discovered. The place was lit up, though Alex wasn’t exactly sure how. He could see vertical tubes here and there that contained bubbling, glowing lava, but he wasn’t sure if they were casting much light or if their primary purpose was for warmth. The constant, slow movement of the globs of lava was quite relaxing and pleasant to watch. Almost too relaxing. Alex felt himself dozing off once or twice but immediately forced himself to stay alert—he couldn’t afford any more mistakes. He studied the layout.

The top level, a good distance below them, was simply a suspended, wood-planked walkway around the perimeter of the glass leading to a single set of large doors. It wasn’t well traveled at all. That’s where they’d seen Sky and Crow’s mother the last time, when she’d told them through Warbleran hand signals that she was a slave. They’d watched her get taken away by a man with gold bars on his shirt.

“What if they killed her?” Sky asked eventually. It had taken her all day to say it out loud, even though Alex knew she’d been worried about that ever since they’d seen her.

No one knew the answer. Instead they tried to memorize the layout of the open areas far below, where large, leafy plants, vegetables, fruit trees, and flowers grew. And there was grass, too, with benches all around. People bustled about the common area, some strolling as if they were enjoying the scenery, others stopping to pick up fruit that had fallen to the ground, still others looking like they were headed somewhere important.

“It’s like they think they’re outside,” Carina mused. “I wonder how often they get out of this cage.”

Alex shook his head. “I don’t know. I can’t imagine they get out very often, except to fish.”

“Oh,” Carina said, pointing, “there goes somebody out the fishing hatch now. See—one glass door slides open to let them into the holding space. When that inside door closes, the outside door slides open and water pours in over them, but they can hold on to a bar so they don’t get swept away. And they’ve got masks of some sort to help them breathe.”

“Shh,” Alex warned. He turned and looked expectantly at the shore nearest them. “He’s right below the ground over there.”

“I don’t think he can hear us if he’s underwater,” Sky said.

Alex felt the blood rise to his cheeks. “I know. I meant in case he swims up to the surface or something.”

Sky elbowed him to let him know she was only teasing. She didn’t like the tension between them. But Alex just gave an absentminded smile and stayed focused on the scene below.

“There’s that playground where we saw all the children,” he said. That glass room was dark now.

The rocks below them shuddered, making everyone tense up. The person who had gone out the fishing hatch came back inside and quickly took off his gear as other people sprang into action inside the island. “I think that’s our cue. We should go,” Alex said. “Now.”

Nobody questioned him.

“Captain, head out to sea immediately! We’ll catch up,” Alex called, knowing his voice would carry nicely over the water at night.

Within seconds, Ahab, who was standing ready, had the ship pulling away from the volcano. The ground shook again, and Alex, Sky, and Carina hopped onto Simber’s back. He took off into the air, and as they passed over the skylight, Alex could see people below scurrying to the walls, where seats dropped down. The people sat down and strapped in, helping children first, then themselves.

“So that’s how they don’t get hurt with all the plunging and resurfacing,” Alex said, pointing. “They feel the warning shivers just like we did, and they strap in for safety.”

Simber started heading for the ship. “Wait a second, please,” Alex said, a bit stiffly. It was uncomfortable speaking to Simber, as it still felt like they were fighting, but Alex couldn’t dwell on that now. “How do you feel about hovering over the volcano while it sinks? Maybe we can see what happens?”

“Yes!” Carina said. “What do you think, Simber? Is it safe?”

Sky looked on with interest. Everybody wanted to know more about the workings of the strange island.

“As long as no firrre shoots out when it descends, we should be safe and hidden frrrom view.”

“And,” Alex said, “we’ll be able to see down into the hole because it’s all lit up. At least until the water covers it. Plus, we’ve never thought to fly over the top to see where that fire comes from.” He grew more excited. “I don’t think it spews any fire at all when it goes down, does it, guys?”