In AD 2122, a North clone billionaire and his family were murdered on St Libra, the tropical planet containing the bio-fuel that is the lifeblood of Earth's economy. Angela Tramelo was convicted of the crime, despite claiming that she was the sole survivor of an alien attack. So when another of the North family clones is murdered in the same manner twenty years later, the Human Defence Agency must send a team, including Angela, to investigate the possibility of an alien threat.