Aidan is a scribe in an Irish monastery on the far edges of remote Christendom. He is content with his life of prayer and meditation and work, even though he was robbed of his royal birthright by the savage Danes. Then he is chosen to accompany a band of monks travelling to glittering Byzantium, to make a gift of a handsome, illuminated script of  The Book of Kells to the Emperor of Christendom. On the journey he will be, in turns, a sailor and slave, a spy and a warrior, a Saracen and a Viking – and he will face the ultimate choice that any man of any age will face: the determination of his fate.