JAM (Christian Clavier), a French "master of the universe" is on the brink of a major takeover when he starts suffering from anxiety attacks. His doctor (Lhermite) thinks it is to do with childhood experiences and suggests he searches back in his mind to something that could be the trigger and will prove to be the antidote.

A briefcase with undisclosed contents – sought by Irish terrorists and the Russian mob – makes its way into criminals' hands. An Irish liaison assembles a squad of mercenaries, or 'ronin', and gives them the thorny task of recovering the case.