In France in 1622, Gil de Berault, the infamous duelist called "The Black Death," reports to Cardinal Richelieu that he has silenced one of Richelieu's enemies. Richelieu is pleased but warns Gil that he has banned dueling and will hang anyone caught fighting. After he leaves, Gil duels in a nearby tavern and is arrested for breaking Richelieu's ban. Gil is nonchalant, certain that his appeal for mercy will be granted, but it is not until Gil is walking the gallow's steps that Richelieu sends for him. Richelieu promises Gil a pardon if he infiltrates the castle of Richelieu's worst enemy, Edmond, Duke of Foix, gains the confidence of Edmond's wife and sister and captures Edmond. To keep an eye on Gil, Richelieu gives him his servant Marius, a quick-witted pickpocket. On a stormy night soon after, Gil throws himself into the river by Edmond's castle, and when he is rescued by the castle servants, he tells them that he was ambushed by bandits. Because he has never met the Foix women, Gil mistakes Marguerite for the duchess and assumes that Elise is Edmond's sister. Marguerite is suspicious of Gil, but decides to keep him at the castle until they receive instructions from Edmond. The next day, she welcomes Count Rossignac and Baron Breteuil, friends of Edmond's who have come to collect jewels to sell to pay Edmond's troops. Later that night, the king's soldiers arrive, and the two noblemen escape via a secret passage without noticing that Marius has stolen their jewels. Breteuil returns the next day, and after he tells Marguerite about the missing jewels, a frantic search begins. Gil and Marius lurk in the woods, trying to find the secret passage, while Marguerite and Breteuil continue the search there. Marguerite sees Gil and accuses him of being a spy, but he returns the jewels, telling her that he found them. Later, the king's soldiers come again and Gil is arrested when he defends Marguerite. Gil escapes, but when Marguerite hears the soldiers shooting after him, she thinks that he has been killed and confesses to Elise that she loves him. After the soldiers leave, Gil returns and tells Marguerite that he loves her when she reveals that she is Edmond's sister, not his wife. Gil and Marguerite spend happy days together until Edmond comes to the castle and Gil arrests him. The next day, Gil, Edmond and Marguerite journey to Paris, but Gil sets his prisoners free. He explains to Marguerite that because he succeeded in capturing Edmond, he fulfilled his deal with Richelieu, but he must return to Paris to redeem his honor. At Richelieu's palace, Marguerite arrives before Gil and begs for his life. Richelieu arrests her, while at the tavern, Marius urges Gil not to go to Richelieu yet, for the cardinal is losing favor with the king and will soon be powerless. Gil says that he must go regardless and is on his way when Richelieu receives a letter from the king, saying that he is pleased that Edmond is in flight. Richelieu realizes he owes his restoration of power to Gil, and so when Gil arrives, he gives him and Marguerite a letter ordering them to return to Edmond's castle. The lovers are overjoyed at the pardon, and as Richelieu eavesdrops on their exclamations, the king arrives.