At the beginning of the twenty-first century, billions of people began to suffer from a strange illness. Many died, but those who survived found themselves transformed, capable of surviving underwater for long periods of time. This new strain of humanity was called the Otom. When a global disaster threatened to wipe out mankind, the Otom fled beneath the oceans, where they have lived peacefully with the Mers, beings half-man and half-fish, for many years. Now, decades after the flood, the radiation is clearing, the planet is healing, and the time is coming when the Otom will return to the surface of the Earth. But the Otom are not the only legacy of the human race. Across the surface roam the vicious Cunmen, their bodies and minds blighted by radiation. And, as they seem to know things only the Otom should, the Otom may have a traitor in their midst . . .

The tsunami that ends mankind's fifth civilisation will travel across the globe, taking all in its wake. There will be those who are swept along on the buoyancy of its joyful surge; there will be those who cough and splutter, clinging to hope as they desperately struggle to stay alive, and there will be those who lie beneath its mighty strength, stilled and lifeless within its power.