The year is 1453. For more than a thousand years the mighty walls of Constantinople have protected the capital of the Eastern Roman Empire, the furthest outpost of Christianity. But now endless ranks of Turkish warriors cover the plains before them, their massive cannons trained on the ramparts. It is the most fearsome force the world has ever seen. No European army will help: the last crusaders were cut to pieces by the Turks on the plains of Kosovo. Constantinople is on its own. And treachery is in the air. Three people will struggle to determine the fate of an empire: the young Turkish Sultan, returned from exile and desperate to prove his greatness; a stubborn Byzantine princess, sworn to protect her city; and a mercenary captain with a personal score to settle. But of them, it is the hardened soldier Giovanni Longo who will face the worst choice: just as he prepares to make his final stand, he finds he has something to live for after all.