“I was always ingenious,” he said, irritated.

“No doubt. But in this case, I’m not sure it would work.”

“Your mechanical pilot will be able to calculate these things, I am sure.”

She smiled. “I thought you didn’t like how dependent we are on our machines.”

“But you are whether I like it or not. And no matter where you go. And so, as you said, you have made them strong. Maybe strong enough for the inside of Io.”

“Maybe.”

She tapped away, while also talking to interlocutors elsewhere. A voice murmured in a language Galileo did not recognize.

Eventually she barked a short laugh. She piloted the craft down onto the burning lake, landing with a final little tilt back, like a goose or a swan.

“So I was right? The ship won’t burn?”

“Yes. No.”

She tapped on her pad, which reminded him of a spinet’s keyboard. Their craft sank into the lake of fire. Having been a space craft and a submarine craft, it was now a sublithic craft, a subsulphurine craft.

“The heat is apparently not as extreme as it looks,” Hera said, as if reassuring Galileo. “Molten sulphurs aren’t as hot as the basalt farther down. The craft has found that compared to Jupiter’s radiation, the protections required are not significant.” She shook her head. “You have to understand, people only began inhabiting Io when I was young. Before that the counterfields weren’t good enough. So the idea of going inside the moon hasn’t really occurred to anyone. Although apparently robotic research craft have already been down here, mapping Io’s internal flow patterns. So we’ll use what they found.”

“Can you make this whole room like a window again?”

Again she shook her head, trying to look amused. “If you like.” Suddenly he saw; she thought he was too ignorant to be afraid, while she, knowing more, was rattled by their situation. Making it look as if they were inside a clear bubble in the sulphur magma would not help her nerves. The Ionians were afraid of Io, no doubt with good reason. But he was pretty sure he remembered enough of Aurora’s lessons to judge their safety better than Hera could. At their levels of material and field strength, melted rock was not a difficult habitat.

She changed the walls of their chamber into a continuous screen, and now they seemed to float like a soap bubble in a liquid mix of yellow, orange, and red—the false colors arranged to indicate heat in a way immediately comprehensible. Patches of bright red flowed by their bubble’s ovoid space, darkening the angriest oranges, which shaded into the most violent of yellows. In theory it should not have been any more alarming to descend through molten rock than through frozen ice. But in fact it was.

“So your ship will follow channels to the underside of Loki, where we will get shot out of one of the sulphur plumes?”

“Yes.”

“And then?”

“We will disable their base’s power plant. That will force them to use their ships to power their settlement. Their ships will thus have to stay on Io.”

“You plan to disable their power plant? That’s all?”

She appeared to think he was being sarcastic. “They’ll be all right. Their ships will serve as emergency power. All will be well with them, but the ships will be confined to their base.”

“Couldn’t you disable their ships directly?”

The light surrounding them shifted all over the fiery portion of the spectrum, washing Hera’s face in color and making it appear as if she were in turn scowling, grimacing, frowning, glaring.

“You don’t understand,” she said at last. “Not all their ships will be in their settlement at any one time, and I want to create a situation where the ones on hand have to stay put.”

“But the ones at large will still be at large.”

“We think most will be on hand. And Ganymede is there.”

Their craft shuddered underfoot, canted to the side. The flowing ribbons of color on the screen had the look of a current, in which their craft struggled to make its way upstream. But the feeling of motion, which came entirely from tiny shifts underfoot, was now a confused juddering that did not add up to a coherent picture of progress in any given direction. Galileo guessed that first they had been falling toward the center of the moon, but were now bumping liquidly along, making their way against resistance. Then it seemed they were rising like a bubble in water, shimmying from side to side as differential resistances caused little horizontal slips. He put his hand to his chair, feeling unsettled almost to the point of nausea.

“Up?” he asked.

“Up. And I’ve got some of my cohort meeting us inside here. We’ll all come up together.”

The drag downward correlated with an acceleration of the yellow flow around them. Hera rubbed a fingertip over her console, watching the flow around them closely as she did.

“Hold on,” she said.

Galileo held on. “Won’t they notice us?”

“They’ll be assuming any approach will be visible,” Hera said, “and some of our colleagues are making an approach from space, to serve as decoys. There are no weapons per se in the Jovian system, as I said, but of course various lasers and explosives can be adapted to the task. We’ll hope that doesn’t go too badly for our decoys, and jump them from behind. This will be the first time they have been attacked from out of the plume of a nearby volcano.” She laughed.

Then he was shoved down at the floor, and understood that they were accelerating upward. The flows around them stabilized to pure yellow. It was like being inside a marigold, and he supposed that this meant they were now moving with the current they were in, but that the magma itself was accelerating in its channel as it approached its release into space. The push down increased in proportion to their speed upward, he was quite sure, even without the knowledge Aurora had given him. He was distracted for a moment as he tried to integrate the sensation with what he had learned during the alchemically enhanced lesson.

The pressure down became stronger. For a moment his body felt some bone-deep familiarity, and he realized they were in exactly the pull of the Earth, and he was feeling his true weight. But quickly he became heavier still—so much so that he let his head rest back in his chair, to keep from hurting his neck. Hera shifted the walls back to their usual gray, and the colors of the flow around them returned to the screens, some of which were filled with color, others with rapidly changing columns of numbers, but none gave him a sense of what was going on. He said, “Can you not display some sort of map that tells us where we are?”

“Oh, sorry. Of course.”

She tapped her console, and the screen in front of Galileo suddenly became like a cabinet holding a little Io. A green thread running from its interior to its surface pulsed brightly from within a tangle of orange intestines. Then the screen changed again, and he was looking at a cross section of the moon that cut the chimney of their volcanic channel, and the widening at its throat. Midthroat, a small cluster of bright green dots rose swiftly. “Your colleagues have joined us?”

“Some of them.”

Then the downward pressure ceased, and he even felt that he might float up and away from his chair, as when they were between moons. A push from below returned, very slight; then nothing; then a slight pressure from above. Hera tapped quickly, and suddenly the walls of the craft became a screen surrounding them again, giving them a view as if they flew freely in space. They were vaulting upward, already many miles above Io. Then they were arcing over the tawny fluxions of the surface. Loki Patera lay beside them and below, and the sulphur mist surrounding them was dotted with the silvery ovoid carapaces of the other ships in Hera’s fleet, floating down like spores after a mushroom explodes.

The fleet stayed in the drift of sulphur slurry, arranging itself as it fell until it was a phalanx, dropping in synchrony with one particular plume of the sulphur. Then in the final drop to the marigold slag on the lower flank of Loki, the whole fleet shot sideways out of the sulphur rain with startling rapidity, and in several heartbeats landed on the perimeter of a small cluster of buildings, apparently Ganymede’s Ionian base. Some of the craft blazed fire as they were touching down, striking buildings in the base and causing brief explosions that seemed as tiny as sparks against the backdrop of the stupendous plume of the volcano.