In 1204 the glorious Byzantine capital of Constantinople is brutalized by the knights of the Fourth Crusade. Amid the devastation, Emperor Frederick Barbarossa crosses paths with Baudolino, a youngster with curious intellectual gifts. Charmed, Barbarossa adopts Baudolino and sends him to to a university in Paris. With the friends he makes, Baudolino begins a quest for Prester John, a legendary priest-king whose fabled empire may hold the secret to the Holy Grail.