Moanna Morgan had never seen the sky. No-one from the Tethys Colonies had, not for a thousand years. Not since the Old Earth died and the world of Thalassa was born, a new world beneath the waves. Submarines sank all the time out in aqua incognita, beyond the Federation Frontier, and Moanna’s brother had been dead for nearly a year. But was the wreck that was found really his? And if not, where did he go, and who would fake it? A chance discovery sends Moanna on a journey into the unknown. There she comes face to face with a secret that has remained hidden through all the ages of Thalassa, and she unleashes a threat that could destroy everything she knows.