Gillian sat erect as she examined her approaching parents. "Mum, Dad! I haven't seen you out here before!"

"Haven't you, Dear?" her mother answered. "I'm sure we must have, from time to time." Her parents stopped at the side of the pool. Mrs Berry said, "This is nice!"

So far as Gillian knew, her parents had never left their small cabin. She was more than surprised to see them outside. It made her nervous. Why should they suddenly do this now? Was she imagining a glint in her mother's eye?

Her father said, "We just thought we'd have a stroll, before I go off to work."

Mrs Berry smiled at her husband. "You're on holiday, remember, Dear?"

Mr Berry looked surprised as he glanced at his wife. "Oh, yes - of course I am!" He gazed around him, his face interested. Gillian's mother winked at her.

"Where does the path lead?" her father inquired. "I must have forgotten."

"It goes right around the second wheel," Abel replied.

"The second wheel..." Mr Berry said.

"You know, Dear," his wife said, "the second wheel of this ship, the Xinglong Hao!"

Gillian glanced at Abel and saw his shocked expression. Her mother remembered where she was.

"Oh, yes - so it does!" Mr Berry said, though his face looked confused. He smiled at Gillian and Abel with an apologetic expression. "I don't understand what's happening to me these days. I think I'll forget my own name soon!"

Abel whispered to Gillian, "Should I notify Dr Morris and McWhirter?"

"I think so," Gillian whispered back.

"What are you two muttering about?" Mrs Berry inquired.

"Sorry Mum, Abel was just reminding me of something we have to prepare for tomorrow, when we're back at work with Liam, the new Walker."

"Oh! That sounds interesting! Could we come and watch, I wonder?"

"Er, we'll need to check first, Mum."

"Would you, Dear? We'd so like to see what you do."

Abel contacted McWhirter to inform him of the new development. He and Doctor Morris soon arrived to examine Mr and Ms Berry. Both men looked nervous and startled.

"Mr and Mrs Berry!" McWhirter said. "It's good to see you so active!"

McWhirter glanced at Gillian as he spoke, and nodded, almost imperceptibly. Gillian saw the shock in his eyes.

Gillian's mother replied, "It must all be due to the nurse that was so kindly organised for my husband and me. He brought an exercise machine, and that and his physio work on us seems to have done us a lot of good quite quickly. It's really woken us up!" She smiled at her daughter. "And having Gillian with us has been so wonderful!"

Mr Berry added, "We were hoping to watch our daughter while she's at work! We're very proud of her!"

"Is that satisfactory to you, Mr McWhirter?" his wife asked.

"I'll check with the Captain," McWhirter replied.

The next morning, McWhirter and Dr Morris met Abel, Liam and the Berry family at Pool Ten. Gillian had already changed into her Walk suit.

"Oh, Gillian, you look so slinky in that outfit!"

"Thanks, Mum."

Liam stepped forward, put down the little pack in which he carried his Walk suit, and introduced himself to Gillian's parents. "Hello, I'm your daughter's pupil," he added.

"Pleased to meet you, Liam!" Mr Berry said. They shook hands.

"Is Gillian a good teacher, Liam?" Mrs Berry inquired.

"She's very good." Liam glanced at Gillian. "She's strict, too."

Dr Morris said, "Mr and Mrs Berry, I wonder if I might give you a brief medical examination? I've brought some special equipment with me."

Gillian's parents glanced at each other. Mrs Berry said, "The nurse did that the other day, Doctor."

Gillian raised her eyes at Abel. Her mother remembered something that had happened on a previous day.

"Well, this is something different, a little extra. I want to take a quick electro-encephalograph reading of each of you. It'll only take a few minutes."

"Oh, well, of course, Doctor," Mrs Berry said, her face smiling in an apparently relaxed manner.

Dr Morris took out her equipment, a small box with a wand connected to it. She waved it over Mrs Berry's head, then over Mr Berry.

"Is that all?" Mrs Berry asked.

"Yes, thank you, Mrs Berry." Dr Morris examined the instrument's readings, glanced swiftly at McWhirter, then bent to stow the instrument and the wand.

"I hope you don't spot any problems with us, Doctor. I must say, we're feeling particularly well at the moment!" Mrs Berry glanced at her husband, who nodded.

"That's good," Dr Morris replied.

"Time to head off and get to work?" Abel said.

Now quite a large group, they all walked over to the path and began their stroll around to McWhirter's temporary Navigation Centre. Gillian noticed that Doctor Morris took care to walk alongside McWhirter. The two began a quiet conversation.

In the small area where the temporary Walk stage and its equipment had been installed, Liam disappeared behind the blocky outline of the simulator to get changed. It did not provide much cover, and Gillian was always amused to see his bare arms and legs jerking into view from behind it. She hopped up onto the stage and squatted on her heels, fiddling with her mask. Abel leant against the simulator to speak to Liam. Gillian's parents sat together on couple of folding chairs.

Gillian turned to look at McWhirter and Dr Morris. When Dr Morris glanced in her direction she raised an eyebrow at him. He nudged McWhirter and they came over to her.

"What do you think?" Gillian asked them.

"Well," Dr Morris replied, "it's certainly possible that a sudden change of scenery, and physical exercise can have a remarkable effect on this brain. They've had both."

His voice trailed away, and Gillian looked what McWhirter. "But?" she said, in an inquiring tone.

McWhirter said, "We'll certainly be watching them closely. I can't see that they can do much harm at the moment - or you, for that matter."

Abel and Liam returned together. 

"Ready to go, Liam?" Gillian asked.

"Sure!" Liam glanced around at his little audience, his face cheerful, and jumped up on to the stage.

Abel said, "I've set up an exercise for you, Liam. It's an area of space crowded with macro-quantum objects." He glanced at Gillian. "He'll need to be able to rotate his reference frame and change scale if necessary, to find a way through."

"I hope I won't run up against anything as difficult as the Wall!" Liam said.

"No, you won't," Gillian replied. "I understand Mr Dryen and Mr Morris have introduced you to the basic gestures for these activities?"

Liam nodded. "It all seemed pretty straight-forward."

"Did they warn you of the dangers?" Gillian asked.

Liam gazed at her. "Yes. They told me about your incident."

"Good," Abel said, "Let's get to work."

Liam pulled his mask over his head. Gillian stood, pulling her mask on to enter the simulation with him.

"Hey!" she exclaimed. "We're back in the clouds outside the bubble!"

Abel said, "I brought it up from the recordings. I thought Liam should see how bad it can get."

Liam said, "Wow! I never realised it was like this!"

Gillian, standing next to him, surveyed the grim, cluttered scene, the same one she had encountered when she first went live in the clouds beyond the bubble. She recognised what a good idea this location was. Even if Liam were clumsy with his gestures while rotating his reference frame, his risk was low. The clouds were so thick that he might not be exposed to enormous depth perspectives, protecting him from vertigo trauma.

They began. Observing, Gillian was pleased to see that Liam seemed to have improved his gait, obviously making an effort to stay conscious of his bodily movements. His style of stepping had improved. That did not, however, prevent him from succumbing to the same trap that had caught Gillian. He fell at a hidden cloud clump lurking at the bottom of an apparent gap between cloud clumps.

"Shit!" he yelled, as he thumped down on the stage.

"Never mind," Gillian said. "Pick yourself up and carry on, Liam." At the same time, she heard horrified gasps from the small audience, and realised that it was her mother and her father. She pulled off her mask and stared at them. "Mum? Dad? What's the matter?"

"Oh, he fell!" Her mother cried. "That's terrible!"

Gillian noticed that her father appeared equally shocked. She was about to ask them the reason, but McWhirter jumped in first.

"Why does that upset you so much, Mrs Berry, Mr Berry?"

They both turned to him, their faces agitated.

"It's just so bad, so wrong for that to happen!" her mother cried.

"Why, Mrs Berry?"

"It's so dangerous for the ship, you understand that!"

"I do, Mrs Berry, but how do you know that?"

For a moment, her mother appeared disconcerted, then recovered herself. "I'm not sure, really, I suppose we must have seen it on the Ship news. It must have been mentioned when they were covering Gillian." She turned and looked at Gillian for support. "That must be it, don't you think, Dear?"

"I suppose so," Gillian admitted.

Gillian and McWhirter nodded. But Gillian was sure that her parents, in their previous state, had not been capable of understanding the Ship news. Now, somehow, they were aware of the dangers for Walkers, and potentially for the ship, if a Walker was unlucky or clumsy.

Gillian directed Liam through the reference frame exercises that allowed Walkers to change their relationship with the surrounding space, so that what had been vertical could be made horizontal, or larger or smaller.

"Slow and cautious, Liam!" she reminded him.

Liam followed the sequence originally used by Gillian during her training: an easy horizontal rotate, then scale changes, and finally the vertical rotations. Gillian focussed on the low-geared gesture that she had been taught: one vertical palm, with an imaginary dial to be rotated with the fingers of the other hand. Liam completed all these exercises successfully. As he performed the actions, Gillian, whose suit was tethered to Liam's so that she saw his instrument readings, monitored the results. She was nervous, conscious that if he made a mistake he could expose to her to the same dreadful perspective that had put her in hospital previously. She was ready to disconnect him at any sign of a problem.

At the completion, Gillian said, "That was all good, Liam: nice and smooth."

Abel said, "I agree. You did well, Liam."

"And the alternative method, where I rotate my hands around each other?" Liam asked.

"Not now, Liam, maybe later."

"That's the dangerous one isn't it? Where things happen quickly."

"Yes. We may disable it for safety."

"Because you think I'm too clumsy?"

"Yes, Liam."

Gillian saw Liam's hooded figure, outlined against the clouds and the few faint stars, nod its head slightly.

"Ok, Liam?" she said. "Lets do some more Walking."

"I wish I could dance across these things like you, Gillian."

"Never mind, just Walk for a while. Get some practice in."

"Ok."

Gillian watched him, feeling distracted, worrying about her parents. But she saw that Liam had learnt from his last fall. He concentrated on making his steps safe and relaxed, trying to use the ballet walk she had taught him. He didn't try to be fast.

A voice cut into her thoughts.

"Gillian, it's Doctor Morris. I'm talking to you on a private channel. If you can hear me, nod your head a little. Don't speak."

Gillian responded with two gentle, slow nods.

"Gillian, I need to inform you that both of your parents, from my analysis of the preliminary electro-encephalograph readings, appear to possess the Walking capability. It wouldn't be too surprising if it were only your mother or your father, since you must have inherited at least some aspect of the ability. But for both of them to have it seems highly unusual. Again, don't speak."

Gillian gave an almost imperceptible nod.

"Of course, Gillian, the most astonishing thing is that we thought their dementia was irreversible. Yet now, they seem to be recovering. McWhirter and I are taking them away for further examination. Don't be concerned when you find they're not here when you and Liam finish up."

Gillian, her heart racing, gave another imperceptible nod.

At that moment, Liam said, "Gillian, can I watch you try Walking through these clouds, please? It might help me."

"Good idea, Liam!" Abel said.

Walking through the cloud clumps to show Liam how it was done was difficult, while Gillian was worrying about her parents. Once, she wobbled and nearly fell, then recovered quickly.

But Liam was full of praise. "That's beautiful, Gillian! You're a master!"

When they finished, she slid her mask off and looked around. Her mother, McWhirter and Dr Morris had gone.

Abel said, "Sorry Gillian, they took your parents away. They didn't say why."

Gillian made an effort to seem surprised, but her expression was really one of worry: at what might befall her parents. She asked, "Where to? Back to the main wheel?"

"No. The second wheel hospital. Where they kept you."

Liam pulled his mask off. "They took Gillian's parents away?" he asked. "How could they be a problem?"

Abel didn't answer. He just added, "They called in two marines as an escort."

When Gillian said nothing, Abel continued, trying to be reassuring. "But it can't be too serious. They just have to be thorough, I suppose, since your parents seem to have changed so fast."

As Gillian's silence continued, both he and Liam stared at her, their faces uneasy.

"Are your parents alien beings?" Liam asked. "How?"

"They're no more alien than I am," Gillian growled. She said to Abel, "I want to visit that hospital."

"What, now?" Abel asked.

"Yes."

Abel, reluctantly, and Liam, enthusiastically, followed her up on to the path, where Liam tripped and fell. Gillian and Abel glared down at him.

"Sorry! Sorry!" he said, jumping to his feet and brushed himself down.

They walked around to the hospital. At the entrance, two marines halted them.

Gillian demanded: "I want to see my parents!"

"Sorry, Miss," one said, "you can't go in." The marine seemed taken aback, even slightly intimidated, by Gillian's appearance in her tight Walker skin suit.

Gillian gave him a push. "I have a right!"

"Don't do that, Miss."

"Then let us in! Do you know who I am?"

"I do, Miss."

"Then you know what I am too..." Gillian tried to rear menacingly at him. But she wasn't as tall as he was.

"Gillian!" Abel hissed behind her. "Don't be silly!"

Gillian thought she glimpsed a slight smile on the marine's face looking down at her. She turned irately towards Abel, just as the marine put a hand to his ear and cocked his head a little.

The marine said, "Ok, you can all go in." He and his companion stood aside.

McWhirter was waiting for them. "Come with me," he said. They followed him up a short flight of stairs and into a ward like the one Gillian had been confined in.

Her parents reclined in a couple of seats, sipping coffee. Doctor Morris sat next to them.

"Mum, Dad!" Gillian called out.

"Hello, Dear," Her mother said, as Gillian found a chair and Liam went and got two more for himself and Abel. "Mr McWhirter here's been quite worried about us."

"Why, Mum?"

McWhirter was behind them. "Because, Gillian, they appear to be in the same condition as you. They are, somehow, under the influence of an alien civilisation."

Mr Berry looked irritated. "The man's out of his mind!" he said.

"And they both have the ability to be Walkers," McWhirter added.

"It's so exciting!" Mrs Berry said. "I'd love to try it!"

"Other than being Walkers," Gillian said to McWhirter and the Doctor, "why do you believe they're under the same alien influence as me?"

Doctor Morris answered. "We've given them detailed EEG and other forms of examination. They show exactly the same abnormal characteristics we observed in your brain while you were in this hospital. You weren't conscious when we took those readings, and we didn't tell you about it at the time."

"So we're all aliens?" Gillian said.

"That's much too simplistic, as you probably know," McWhirter replied. "We can't tell the extent of the alien influence on you, how it might make you behave, and if it can be transmitted from you to others."

"So: what do you propose to do with us?" Gillian asked.

"I never heard such drivel!" Mr Berry grumbled. "Aliens - me and my wife?"

"What do you want to do, Mr McWhirter?" Gillian repeated.

McWhirter sighed and pulled up a seat. "This may be the most momentous time in human history: our first contact with a non-human civilisation. Not only that, we now know from you, Gillian, that even our home system has alien artefacts installed within it. One of them is responsible for Mr Yegg's disability. The Captain I, and the other officers, must consider the security of the ship in the light of this development."

Abel asked, "Aren't there standard policies set down in the event of such an encounter?"

""Well, there are. But all that's ever been found of alien civilisations are their ruins. It's accepted wisdom that we're either too far away in space from alien civilisations, or too far apart in time, so there's no point. We never coincide. The policies have never been taken very seriously."

"Yet now here we are," Gillian said.

McWhirter nodded. "And you're not exactly alien are you? Other than keeping you under restraint here in the second wheel, I don't have any good ideas. You all seem like nice people."

"For aliens," Gillian said, her voice sarcastic.

"Right."