Gatún Lake. They moved under a slightly hazy sun, through the vague shafts of cloud shadows, with the land starting to shimmer on each side and the V of the ship's bow-wave breaking against the shores further and further away.

They cleared Barro Colorado, leaving the island nature reserve behind to port. There must have been a little tension on the bridge after all, because she noticed that people talked a little more now they were past the section the two tankers had been attacked in.

They were in the main part of the lake now. Ahead of them, across the sparkling waters of the lake, its lines sharp and definite against the jumbled greenery of the lake's scattered islands, lay the lone tanker the authorities had told to remain there while the current emergency existed.

It was French, registered in Marseille, and called Le Cercle.

They didn't hear or see the explosion at Gatún, but the VHF call came through just as they were passing the moored tanker, and the masts of another ship — the Nadia — were appearing over the trees of Barro Colorado island, behind them.

They'd told her, her mother had told her, Mr Kawamitsu had told her, but she hadn't thought they were serious; she had to leave her mother and go to live in Tokyo to attend the Academy. For months, whole seasons, at a time. She was twelve. She didn't think it was allowed to desert somebody who was just little, but everybody seemed to think it was for the best, even her mother, and Hisako didn't even hear her weep the night after the confirmed offer of the bursary and place came through. Hisako looked at the palms of her hands that night — it was so dark she wasn't sure whether she could see them or not — and thought, So this is the way the world works, is it?

She felt oddly remote from her mother over the next few months, and really didn't seem to feel very much when she was taken to Sapporo station to board the train. She was looking forward to the ferry journey; that was about it. Her mother was embarrassingly emotional, and hugged her and kissed her in public. As the train pulled out, Hisako stayed at the carriage door, face expressionless, waving goodbye, more because she felt it was expected of her than because she wanted to.

At the Academy everybody seemed cleverer and wealthier than she, and the cello lessons very basic. They were taken to hear the NHK; she preferred it when there wasn't a cello work on the bill, because when there was she couldn't help listening to learn, rather than just to enjoy. On Sundays the hostel children were usually taken round an art gallery or museum, or into the countryside; Hakone, Izu, and the Fuji. Five Lakes, which was much more fun. She got to climb things and go on ferries.

To her dismay, the Academy teachers were just as scathing about her academic performance as the teachers in Sapporo had been. She remained convinced she had actually learned vast amounts throughout her life, and they were just asking the wrong questions. She came top in English, about average in her cello class, close to bottom in everything else.

Hokkaido was clean and clear and empty after Tokyo, on her first vacation, and fairly deserted and unspoiled even compared to the countryside west of Tokyo. Her mother took her walking in the woods, like in the old days. Once, the two of them sat beneath some pine trees overlooking a broad valley, watching the warm wind stroke slow patterns across wide fields of golden grain beneath them, and the tiny dots of cattle moving on the green swell of a hill on the far side. Her mother told her how she'd cried the night Hisako had left for Tokyo, but that really, she was sure, they were tears of happiness. Hisako felt ashamed. She hugged her mother, and put her head in her lap, though she did not cry.

She coped with Tokyo, she mourned for Hokkaido. Sundays were still her favourite days. Sometimes a group of them was allowed to go out without a teacher. They said they were going to museums but they really went to Harajuku to watch the boys. They strolled down Omote-Sando Boulevard, trying to look mature and sophisticated. Hisako's command of English began to be admired. She still came top in that, and her other grades were improving (not that that would have been difficult, as all the teachers pointed out), and she won a prize in the Academy's cello competition. She'd never won a prize in anything before, and enjoyed the experience. She wanted to use the small amount of money involved to buy some new clothes, but her mother's last letter had talked about a part-time job in a bar, so she sent the money home instead.

Another year; another too brief visit home to Hokkaido. The pace of Tokyo life, the urge to do as well in exams as any other child but to be a musical prodigy as well, even the regularity of the seasons; cold, mild, hot, stormy, warm; Fuji invisible for weeks then suddenly there, floating on a sea of cloud, a flurry of cherry blossom lasting hardly longer than a pink snowstorm… all seemed to conspire to sweep her life away from under her. Her grades went on improving, but the teachers seemed to make a special effort to remind her how important they were. She read novels in English; book in one hand, dictionary in another. She won all the Academy's cello prizes. She spent some on clothes, sent the rest home. She was getting used to the remarks about having a cello between her legs.

The Academy offered her a bursary for another three years; somehow she'd expected they would, but she didn't know whether to take it or not. Her mother said she must; Mr Kawamitsu said she must; the Academy said she must. So she supposed she had to.

Philippe had hoped there might be fish in the lake that would be attracted to their lights, as well as simply desiring the novelty of diving at night. So far, in their day-time dives, they had seen hardly any fish. The aquatic life in Gatún Lake had suffered twice over. First there had been a series of algae blooms caused by fertilisers washed down from the distant hills around Madden Lake and the far western shores of Gatún itself; then the fish and plants had been affected recently by deforestation chemicals used in the early stages of the war. The scientific station on Barro Colorado said the lake was safe to swim in again, but the plant community and fish. stocks were recovering very slowly.

Philippe's blue flippers waved back at her. The lake felt warmer than it did during the day, which surprised her. Perhaps it wasn't really any warmer; perhaps it just seemed so because she expected the dark depths to be cold.

The sense of placelessness, of being contained and cut off yet somehow free as well, was intensified by the darkness. With the day's silvery surface removed, the limit of visibility became what their lights could illuminate, and the lake felt both tinier and greater than it had before; tinier because at any moment they could see only a short distance around them, and so could have been swimming in some small pool, but greater because there was no immediate way of telling the surface was not far above, and the floor not far beneath.

Using the lights, the lake waters became like some swirling and disturbed version of space; in the white beams of their lamps a galaxy of minute particles was revealed, each mote glowing against the darkness like a swiftly passed star. Colours were more vivid, too, though there was little enough to see; just the blue of Philippe's stroking flippers and the bright orange of the line he was paying out behind them, to lead them back to the Gemini. She pointed her lights straight down, and saw the floor of the lake gliding greyly by, smooth and ghostly and quiet.

The National Guard reported there had been a venceristas bombardment of Escobal and Cuipo, followed by a retaliatory strike by Panamanian Air Force jets. This was the official explanation for the fireworks on the night of the Nadia's party. The incident made the Channel 8 news, briefly. Reading between the lines, it appeared as though whatever had first happened hadn't warranted the pyrotechnics they'd seen unleashed.