Chapter 1

      THE PIRATE’S DAGGER

      Sometimes the smallest decision can change the way things turn out. For example, one afternoon a hammerhead shark decided to visit the reef around Monpetit Island. If its instinct had led it to find dinner elsewhere, the world might now be a cold, dark place with very little life on it.

      As it happened, we had a narrow escape. But for the shark, it turned out to be a very bad choice.

      The warm water of the Indian Ocean is home to all kinds of creatures.

      Almost exactly in the middle of this great mass of water just south of the equator, a group of tiny green islands basked in the sun. The sea here was shallow and still. If you were standing on the deck of a passing ship – sailing, say, from Madagascar to India – you’d find water so clear that you could see the world beneath. You’d see shadows of large creatures making their way over the veiled sea floor, like planes crossing the skies of the world above. Maybe a school of flying fish would pierce the surface to surprise you, and leap up into the air before they disappeared again into the mysterious depths.

      Where it was shallower, coral reefs formed dark patches and sandbanks turned the water a brighter blue. Dolphins played in the waves, and sometimes you could spot the reef’s colourful fish swimming below.

      If you were lucky enough to live on one of those beautiful little islands, as Anna did, you’d have summer throughout the year – you wouldn’t even need to keep winter clothes. You’d never have to be careful crossing a busy street in peak traffic, and you’d never run out of games to keep you busy on lazy afternoons.

      On just such a Thursday afternoon, Anna had gone swimming in the shallow water surrounding Monpetit Island. She was inspecting her collection of sea slugs, which she kept in a natural aquarium on a coral reef. It was already late and she’d only just returned from school after a long, boring day.

      Sea slugs are beautiful snails without shells, and some of them are more colourful than butterflies. Like miniature dancers, they twirl their bright, frilly skirts over the reef. Anna collected different kinds of sea slugs from all over the islands and kept them in her submerged sea garden, where they grazed on sea sponges and anemones, content in their small world.

      Even in the fading light, the coral reef was colourful – the last beams of the setting sun sifted through the clear water and brushed the backs of bright tropical fish. Anna always felt at ease in the ocean. She felt the heat of the day leaving her skin as she glided through the cool water. Here, she could forget the voices of her teachers and school friends. This was her world, a space of filtered light and muted sound.

      Anna slowly kicked her flippers and gracefully propelled herself through the warm water. She knew the names of most of the creatures that lived here. As she swam through a school of small fish, she counted their stripes: five dark horizontal stripes, and a yellowish hue over their backs. These were called “sergeant majors”, and there were a lot of them around. To her left, a long yellow trumpet fish floated lazily over a giant anemone, and a cloud of small Blue Petes patrolled a rock covered in bright sponges and sea stars.

      She didn’t spot him, but from his resting place under a huge mushroom-shaped coral, a sleepy hawksbill turtle watched Anna with hooded eyes. She didn’t look hungry or dangerous, he decided, and slid back to his lazy dreams of lady turtles and long voyages through the open sea.

      Anna had learnt to swim before she even could walk. She knew how to use sea currents and her own natural buoyancy to glide as gracefully as any fish. But there was something unusual about this girl swimming along just under the surface of the tropical ocean: she had no snorkel or scuba gear, but she never broke the surface to breathe.

      How was she doing it?

      To answer this question, we need to understand a bit about Anna’s family. Her parents especially. They were no ordinary parents: they were scientists. And they were no ordinary scientists: they worked for a society that controlled the most advanced technology in the world, ever.

      Because of a few of her scientist parents’ clever gadgets, Anna didn’t need bulky diving gear to see and breathe underwater. Instead, she was wearing a pair of purple waterspecs that fitted snugly around her eyes. The mask was much lighter and smaller than an ordinary diving mask, and it gave her a perfect 180-degree view of the underwater seascape. She also had a small aquabreather in her mouth. Her father had developed the aquabreather years before, when he still lived on Earth. It worked in the same way as the gills of a fish, allowing her to suck breathable oxygen directly from the seawater, and letting the oxygen-stripped water out again through two small vents at the side of her mouth.

      She didn’t need any tanks to be refilled. This way of breathing automatically equalised the pressure in her inner ears, and as long as she didn’t go too deep, she didn’t even need to make decompression stops when she returned to the surface.

      She could stay underwater for hours!

      Monpetit Island is just eight degrees south of the equator. In the tropics, the days are always the same length of time. The sun always seems to be right above your head until just around six o’clock, when daylight suddenly fades. The sun dives quickly towards the horizon, its last rays painting the sky orange and pink.

      And that is exactly what was happening now. As the sun set, the reef’s bright colours faded into soft blue shadows.

      It is not such a clever idea to be in the water at early dawn or at dusk. This is the time when hungry sharks often come from the great depths beyond the reefs to hunt in the shallow water close to the shore. Anna knew this, but she had a problem: annoyingly, during the week she had to go to school for most of the day. And so on most afternoons, as soon as Ton had brought her home in the small motorboat, she would rush out to the water to enjoy a long-awaited swim.

      Ton knew there was no use in arguing with her and trying to stop her from swimming when it got late. The only thing he could do to keep her safe was to fashion a special shark alarm for her, which she wore strapped to her wrist like a watch. The alarm worked like miniature sonar, warning her if any large creature swam too close. It sent out ultrasonic sound waves into the water, and beeped if it sensed something approaching. A small, luminescent picture of the detected creature would then flash on the screen. Usually it was a ray, or sometimes just a turtle.

      Ton was good at making clever things like that. Although he had been working on the island ever since Anna could remember, he’d actually only arrived after the admiral’s accident. Anna’s mother had realised that she would need help raising the children, and she had placed an advertisement for a “general manager” in the local newspaper.

      Ton had been the first person to respond.

      Ton was almost seven foot tall, and he was incredibly strong. His shoulders were like the granite rocks some islands are made of, and his arms were as thick as the trunks of the takamaka trees. His head was shaved, and the skin of his scalp was as shiny as a cannon ball. Despite the tropical heat, he always dressed himself in a black suit, a crisp white shirt and a tightly knotted tie, but he kept his feet cool by wearing blue-rubber slip-slops, each one as big as a small boat.

      Right from the start, Ton had proved to be efficient and very clever. He was a great cook, and often used the coconut from palm trees in his cooking and baking, and he grew his own vegetables. The children loved the way he