To be closer to his children following his divorce, Laurent Monier, a history and geography teacher in a peaceful provincial high school, accepts a position in a sensitive college in the Paris suburbs. He is assigned the hardest class, the fourth techno, and he finds an apartment in the Cité des Muriers, a particularly difficult district.

A sleazy Paris nightclub owner and ex-detective flies to Hong Kong to rescue the young son of a friend murdered by the Chinese mob.