It is the year 48 before the Common Era. In the royal palace on the harbour's edge, Cleopatra VII has just been driven from her throne by the ministers of her younger brother. She will soon return, carried in secret through the harbour mouth, past the great lighthouse on the island of Pharos, its fire burning at the entrance to the greatest city the Hellenistic world has ever built. Alexandria already holds more than half a million souls. Its streets run straight as arrows, its library holds the collected learning of centuries, and its ships carry Egyptian grain to feed the Roman republic. Yet the kingdom is three centuries old now, and the shadow of Rome falls longer each year across the harbour.