Written by Rick Drew; Directed by George Erschbamer
The Musketeers are dropping off their laundry to be washed when they see Mirelle, who went on a date with D'Artagnan and became obsessed with him. D'Artagnan had claimed to be transferred to Brittany in order to get away from her. The others find the situation hilarious. Captain Bernard shows up and berates Mirelle for ruining the ruffles on his shirt. The other Musketeers prompt D'Artagnan to defend her honor, which he does by defeating Bernard in a swordfight and making him apologize. Meanwhile, Siroc finds a scrap of paper in someone's laundry basket, which he recognizes as a fragment of the lost notebook of Leonardo da Vinci.
King Louis plans to send gold to his cousin, François de Mignon, who is fighting with his brother Armand over their inheritance. Mazarin tries to make him reconsider, but Louis resolutely sides with François because Armand stuck a veal chop down his pants once when they were children. Louis tells Duval to assign Musketeers to guard the gold.
Mazarin and Bernard discuss the issue; Mazarin wants Armand to win because Armand is part of his secret Order and they could gain control of Mignon. They plan to intercept the gold. A spy reports that Siroc has found a fragment of da Vinci's notebook.
Bernard captures the man whose laundry the fragment was found in and tortures information out of him.
Siroc examines the paper, trying to figure out what invention it's from, while Ramon looks on with disinterest.
D'Artagnan flirts with Jacqueline. She rebuffs him, partly because she's annoyed at how he treated Mirelle. Duval sends Ramon and D'Artagnan off to guard the gold.
Mirelle asks Jacqueline about D'Artagnan. Jacqueline breaks the news gently that D'Artagnan isn't interested in her, and that she should try to find someone better. Mirelle immediately redirects her romantic attentions towards Jacqueline.
Mazarin, after hearing Bernard's report about the notebook, calls a special meeting of the Order. He announces that an invention in the book could help them win the fight for Mignon, but the only person who could build it is a Musketeer.
Mirelle arrives at the Garrison with a homemade dinner for Jacqueline, which heartily amuses D'Artagnan and Ramon. Jacqueline tries to avoid Mirelle, but agrees to go on a date when Mirelle starts to cry.
Siroc answers Mazarin's invitation and meets him in his office, although he's suspicious. Mazarin says that he and Siroc are kindred spirits, scientists who should not be bound by conventional morality. He offers Siroc a lab with a better budget than the Musketeers.
Mirelle and Jacqueline eat at the Cafe Nouveau. Mirelle is awkwardly flirtacious and touchy. Jacqueline tries to avoid her, which Mirelle takes as a sign that Jacqueline wants to slowly savor their passion before indulging.
At night, Siroc receives a note on a rock thrown through his window. He meets the man who found the notebook, who gives him another fragment and asks him to keep it secret. The next day, Siroc studies the fragment while sitting in the Cafe Nouveau. When he leaves, he overhears Mirelle talking to the man who found the notebook, who turns out to be her father. She claims she's going to marry a Musketeer.
D'Artagnan and Ramon transport the gold.
Mirelle barges into Siroc's lab on the pretense of returning laundry that got misplaced. She asks him to tell her more about Jacques; he answers a few questions tersely before throwing her out.
Ramon and D'Artagnan make camp and are attacked by masked men. They defeat the men and find a note referencing "the great leveller" which will bring victory. They discover a survivor and try to question him, but he commits suicide with foxglove.
D'Artagnan and Ramon announce their successful gold delivery to Louis. Louis feels that he has finally done something successful, and decides to stop trying to play the flute and instead play the more kingly drum.
Ramon and D'Artagnan go to Siroc to help analyze the note. He's not sure what it means. Ramon and D'Artagnan suggest that Siroc join them in some sexcapades, but Siroc says he's busy.
Siroc stays up all night putting together an invention, which he hides when Jacqueline knocks. She invites him to church; he declines, but asks her to pray for him.
Mirelle's father approaches Jacqueline and asks about the wedding. Jacqueline is confused, and says she has no intention of marrying Mirelle. The conversation is interrutped when Jacqueline sees Siroc riding off in a haycart and follows him. Mirelle and her father follow Jacqueline.
Siroc finds a clearing in the woods to test his invention: a hand-cranked machine gun. Jacqueline, Mirelle, and Mirelle's father witness this. After he fires it at practice targets, he freaks out at the destruction and tries to chop up the machine. Masked men stop him; they capture Jacqueline, Mirelle, and Mirelle's father and tie them up to force Siroc to use the weapon again.
Duval asks D'Artagnan and Ramon where Siroc and Jacqueline are. Someone saw Siroc ride off in a haycart. Ramon and D'Artagnan go off looking for them, and encounter a masked man about to kill Jacqueline, Mirelle, and Mirelle's father. Mirelle asks Jacqueline for a kiss before they die; she refuses, which amuses D'Artagnan and confuses Ramon. They dispatch the masked man and free the captives. Jacqueline gives a rude goodbye to Mirelle, which does not diminish her attraction in the slightest.
Jacqueline, D'Artagnan, and Ramon discover Siroc working the weapon again, under threat by the masked men. It's revealed that the Order plans to use the invention to defeat François at Mignon. The Musketeers manage to overpower the masked men.
Mazarin blames Bernard for the loss of the weapon, and whips him as punishment.
Siroc reveals that he dismantled the weapon and hopes da Vinci's notebook will remain lost until a wiser man can find it.
Jacqueline disguises herself as a woman and visits Mirelle claiming to be Jacques' fiancee. Mirelle claims that Jacques tried to take advantage of her and that she never really liked him anyway, which annoys Jacqueline.