Jacqueline, a girl in trouble with the law, dresses like a boy and joins the musketeers to avoid arrest, but she runs into trouble after an argument with D'Artagnan Jr. yet wins the respect of the instructor and two of the other musketeers, Ramon and Siroc. She soon discovers that her brother has been taken by the evil Cardinal to be used for experimentation by a secret society and sets out to rescue him. Along the way, she gains the help of D'Artagnan, Ramon and Siroc, and D'Artagnan discovers her secret.

When a gang extorts money from local shopkeepers, D'Artagnan and Jacques go undercover to find who is behind this ill deed. Meanwhile, Mazarin finds out what the musketeers are up to and tries to frame them for the deed; Siroc creates the "sub aquatic chamber", the world's first submarine.

French noble children are disappearing from their homes in the middle of the night without signs of a struggle, and the musketeers are called in to unravel this mystery. All the while, Ramon is falling under the spell of a beautiful poet and enchantress, who is really in cahoots with the Cardinal and the Secret Order. Their plan is to brain wash the children and then implant them back into society in two years' time.

As her female self, Jacqueline rescues and falls in love with the exiled King Charles II of England, who is on the run from the vicious Oliver Cromwell. He offers to make her his queen, but will she choose to stay to fight for her own country or leave for love?

Siroc builds a machine gun that da Vinci apparently designed before he died. Meanwhile, Jacqueline has to fend off a girl who is obsessed with "Jacques" and is one of D'Artagnan's castoffs.

D'Artagnan's father arrives at the same time that a list of French agents is stolen, and D'Artagnan begins to wonder what kind of man his father has become, when suspicion falls on him. Meanwhile, the Queen begins getting threatening letters.

D'Artagnan finds a baby that he believes is his own, and he and his fellow musketeers attempt to care for the infant. Meanwhile, D'Artagnan has his hands full when he encounters the Highwayman, who is terrorizing people and wooing women.

Cardinal Mazarin tracks down a member of his society who stole a stone from the body of the Black Knight. Meanwhile, Ramon is upset with D'Artagnan over a woman, and they must work together to save her when the Black Knight kidnaps her.

Princess Tatiana of Upper Gaborski comes to France to sign the betrothal agreement with King Louis, but her country's newfound diamond wealth holds a secret. Meanwhile, the musketeers attempt to thwart a plot to kill the Princess.

Ramon is injured by a legendary sword, and when Jacqueline picks it up, she becomes an invincible fighter, oblivious to its powers. Meanwhile, the musketeers must fight to save Ramon from death and recover Jacqueline before the sword steals her soul.

When a man is murdered by Mazarin's men, his brother and widow believe the musketeers to be the culprits, but they soon discover the truth. Meanwhile, the musketeers must keep the woman and her brother-in-law safe for he is the illegitimate son of the late King.

While posing as her female self, Jacqueline, to befriend a woman from Captain Duval's past, she discovers that a man is posing as "Jacques" but unmasking the deceiver could expose her own secret.

D'Artagnan and Jacqueline meet the famous author Alexandre Dumas and in a strange twist he relays to them that he is their creator. Meanwhile, Jacqueline learns her brother is back in France and wants to see her and Siroc creates a love potion which the musketeers test, with interesting results.