Paris 1899. Corporal Jean Albertini (Tahar Rahim), an orphan of humble origins, is chosen to infiltrate a band of anarchists. For him, it's a chance to move up the ranks. But forced to compromise without respite, Jean is increasingly divided. On the one hand, he delivers incriminating intelligence reports to his superior, Gaspard (Cédric Kahn). On the other, he feels himself developing genuine feelings for the anarchists.