Secret agent FX-18 goes undercover to break up an espionage ring.

Arsène Lupin is extremely popular among the population, because he allows the needy to share in his acquired wealth. Before entering the service of the German Emperor Wilhelm II, he removes his vault in Alsace, steals two paintings of old masters, steals valuable gems and calls out to the police prefect to avoid his arrest. But this time he risks being seriously recognized. Lupin must once again use his fine intellect to deftly escape the situation.

An old and poor couple, Charles and Lucie, scrape by working as a concierge and an untalented antique dealer, respectively. But one day, their dreary daily routine is disrupted by the surprising news that they have inherited a luxurious house in the South of France.