Roland Barthes is knocked down in a Paris street by a laundry van. It's February 1980 and he has just come from lunch with Francois Mitterrand. Barthes dies soon afterwards. History tells us it was an accident.

But what if it were an assassination? What if Barthes was carrying a document of unbelievable, global importance? A document explaining the seventh function of language - an idea so powerful it gives whoever masters it the ability to convince anyone, in any situation, to do anything.

Police Captain Jacques Bayard and his reluctant accomplice Simon Herzog set off on a chase that takes them from the corridors of power to backstreet saunas and midnight meetings. What they discover is a worldwide conspiracy involving the President, murderous Bulgarians and a secret international debating society.