“He’s out of your line-of-sight and range. Don’t worry about that. I’ll feed you the Mayfly’s ID and you or your autopilot can do the rest. Wherever he goes, your scooter can follow. You are faster, and you will catch up. Better set collision avoidance.”

“Doing it.” Paul flipped a switch. “Prepared for take-off.”

For Jan that was insufficient warning. Even after her earlier experience, she was unprepared when the scooter reared to a vertical position and accelerated upward — hard. She could not fall, because the seats were gimballed to follow the direction of acceleration, but the change in attitude brought her to an uncomfortable fore-and-aft posture, knees crunched tightly into the narrow space in front of her seat. Her view of the world outside the scooter became a flickering display, with beneath it a slit of transparent panel that looked ahead to an alien field of stars.

“He’s heading inward.” Paul was studying the information panel that ran across the upper edge of the viewing screen. “We’re trailing him, and our path is toward Jupiter. You were right, Jan. He’s back to his old fixation with cloud patterns.”

There was a sudden and surprising interruption. The voice of Rustum Battachariya, so faint and garbled by interference as to be almost unidentifiable, broke in from the wrist unit that Milly Wu had given to Jan. “A fixation with clouds would be acceptable. Regrettably, that may not be the case.”

The unit was not designed for such long-range operation. Bat was fading in and out as he went on, “If Sebastian Birch merely desired to observe… disturbance in Jovian atmosphere… would not have encouraged such immediate action. Unfortunately…”

Jan said, urgently into the tiny unit, “What is he doing? I have to know.”

“I fear that he seeks… atmospheric entry.”

“Why?”

“My apologies… I cannot discuss this. However, you must stop… seek to summon other forces…”

The rest of Bat’s words were lost in a wash of static.

“He’s going,” Paul said. “The wrist unit’s beyond the limit of its range.”

“He says Sebastian is going for Jupiter atmospheric entry.”

“Yes. Again.”

“Paul, we have to stop him. He doesn’t know what he’s doing. If someone can help us…”

“Not feasible.” Paul had turned on a signal detection system to scan the sky ahead of the Flyboy scooter, and a single red speck flashed on the screen. “That’s Sebastian’s ship. There’s no other vehicle in space between us and Jupiter. Europa and Io are on the other side of the planet, they can’t do us any good. Amalthea is in the right position, but it only has cargo vessels ready to fly. It’s up to us.”

“What can we do?”

“So long as he keeps accelerating, not much. We have no way to change his course, no way to disable his ship without killing all of us.”

Paul adjusted a setting, and the broad arc of the Jupiter terminator appeared on the screen next to the flashing speck of red. “It’s going to take a while to catch up, but we’ll be alongside him long before he’s close to the planet. Then I can blanket him with emergency frequency radio signals, and he’ll have to listen — he can’t switch that unit off. It will be up to you, Jan. You have to talk to him. Persuade him to turn his ship around and head back to Ganymede.”

Persuade him? You don’t know Sebastian. But it would be pointless to say that to Paul. Who did know Sebastian? Certainly not Jan, though she had spent every waking hour with him for many years.

She sank back into her seat, staring at the blinking red dot on the screen. It was slowly brightening, but the arc of Jupiter seemed to grow more rapidly. “How much time do we have?”

“Hours and hours, before we are close to Jupiter. But we’re within emergency signal range. You can talk to him now.”

Paul sounded calm and sane. Jan felt neither, but she had to pretend. “Sebastian? Can you hear me?”

She didn’t expect a reply, but the answer came at once. “Yes, Jan. I hear you.”

The words were rational, but the tone was of someone talking in a dream. She felt Paul’s encouraging pat on her suited arm. “Sebastian, the ship that you are flying doesn’t belong to us. We must return it.”

“I know. I’m not stealing it, Jan. I’m just borrowing it.”

“It’s time to give it back. You have to turn around now.”

“Not yet, Jan. Not until I’ve finished.”

“What do you mean, finished? Where are you going?”

“I need to fly close to Jupiter. I need to go to the clouds.”

“Sebastian, if you fly back to Ganymede you can have the use of telescopes that will show you all kinds of cloud details. A swingby may sound easy, but it isn’t. You need to have an expert in charge of it.”

“You don’t understand, Jan. I have a job to do. I must do it.”

“What job? Nobody gave you a job — certainly not one like this.”

“They did, Jan. I know what I must do. I’ve always known it.”

“That doesn’t make sense, Sebastian. We’ve spent almost our whole lives together, and you’ve never talked to me about a job. What is it you have to do?”

“You wouldn’t understand. Jan, I hope you won’t mind, but I don’t want to talk anymore. I’m not going to talk anymore.”

“Sebastian…” Jan felt Paul’s hand on her arm.

“You’re not getting through to him,” he said quietly. “Admit it, Jan. He’s crazy. I said that you had to persuade him, but you can’t persuade a crazy man.”

“I have to try. Let me keep talking to him, maybe I can get through to him.”

“It’s all we can do. As we approach I’m going to bring us right alongside. It may help if he sees our ship and knows you’re with him wherever he goes. Talk to him, Jan.”

About what? But the words came spilling out. She began with their earliest days together, in the displaced persons’ camp at Husvik. She spoke of their schooling, the flower festival in Punta Arenas, summer evenings that lasted forever. Then there was their joint decision to take jobs on the Global Minerals’ platform, the application to move to the Outer System, their plan to work on the Saturn orbital weather station.

Through all of it Sebastian answered not a word. When the two ships were racing side by side, Jan could see the dark dot of his helmet in the Mayfly’s tiny cabin. So near and yet so far away. And as Jupiter loomed large in the sky ahead, she realized that all her talk of “their” plans and “their” actions was delusion. She had proposed. She had persuaded; Sebastian had merely gone along. So why did he refuse to go along now, when she needed to persuade him as never before?

She knew why. Her thinking had not been quite accurate. The interest in the cloud patterns of the outer planets had never been hers. It had always been Sebastian’s, and his alone. That had brought them out to Ganymede. That drove them now toward Jupiter.

Their trajectory was not as Jan had expected. They were flying side by side, but rather than following a path that would graze by the planet, the two ships were arrowing right toward the center of Jupiter’s banded disk. She realized that Sebastian had never said he wanted to make a flyby. He wanted to “go to the clouds.” If they did not change course they would plunge deep into the atmosphere on a path of no return.

Through all her talking, Paul had sat quietly. She was still talking, with a sense of futility and with no response from Sebastian, when Paul said, “Ah! At last. That’s what I’ve been waiting for.”

He manipulated the controls so fast that she could not follow what he did; but suddenly they were in free-fall.

“What’s going on?”

“He’s out of volatiles. I told you, Ganymede Ground Control doesn’t like crew members joyriding too far, so they’re stingy with reaction mass. The Mayfly has no more drive capability.”

“Does that make any difference?”

“A huge difference. While we were both accelerating, nobody could leave either ship without being left behind in space. Now I can go over to his ship and bring Sebastian here. Then we turn around and go home. We still have plenty of reaction mass.”