It is the year 1665. Ever since the declaration of 1666 as the Year of the Beast, the religious have been in a state of anxiety, for the end of the world approaches. It is said that their only hope of salvation lies within an obscure book known as The Hundredth Name. The Koran speaks of ninety-nine names of God, but it is believed that The Hundredth Name contains an additional name which, when uttered, allows the invoker to call upon His protection.
When asked about the book, curio merchant Balthasar Embriaco attempts to persuade his customers that in all likelihood it does not exist. Everything changes when he is unexpectedly given the book. He finds himself selling it even before he has had the chance to glimpse its contents or ascertain its authenticity. Persuaded by his elder nephew Boumeh, he leaves for Constantinople in the hope of retrieving the book. Events conspire against him and he finds himself travelling his journey further afield. In an age of religious and political anxiety he meets all sorts, from religious fanatics and madmen to those who retain their own sense of rationalism.
Among the believers in the coming apocalypse is Boumeh, who is single-minded in his pursuit of the book. Although a non-religious Christian and a healthy skeptic, Balthasar is weak-willed: logic is overridden by anxiety, and he finds his skepticism gently eroded by the murmurings of doomsayers. Against his own advice, and feeling the anxieties spread by the religious maniacs, he finds himself looking for signs that are not there. It's a shame that Balthasar is reduced to using mysticism to explain events, disregarding the sage words of the people he meets on his journey.
On his journey he falls in love with people and places. It is as if the journey has allowed him to live for the first time, experiencing never-felt passions and succumbing to the brash decisions of youth. His journey concludes in guilt and regret about what has happened and what could have been. Little is resolved satisfactorily and the people important to Balthasar disappear. In the end, despite everything he has been through, Balthasar remains unchanged as a person, as if he had been a passive observer all along---a prodigal son making his way back home in a confused world.