Corinne (played by Barbie) is a country girl from Gascony who dreams of being a musketeer in France. She goes to Paris with a letter for Monsieur Treville, the captain of the musketeers and an old friend of her father, hoping to be accepted as a musketeer.
But being a musketeer is not easy for Corinne. She is made fun of, and hired as a palace maid, not a musketeer. She meets her coworkers, three other girls who also dream of being musketeers too: Viveca, Aramina, and Renee. The next day when they return to work, a chandelier drops, and Viveca, Aramina, and Renee show off their musketeering skills. Corinne also finds a small ruby and above finds that the rope has been cut.
An old maid named Helen overhears their conversation and takes them through a secret passageway, where she leads them to the old musketeer training room, and agrees to train the four girls to be true musketeers. Soon the four girls are mastering their skills with Helen's help.
One day, while Corinne is cleaning the windows, she spots the prince hanging from his flying machine and runs to help him. The prince thanks Corinne and later falls in love with her. But later, she finds that the rope has been cut, just like the chandelier!
One night, Corinne, Viveca, Aramina, and Renee decide to celebrate their musketeering skills and walk into the dark, quiet streets. They encounter a man who pulls out a knife, and Corrine realises it matches the ruby she found next to the chandelier. They soon discover that the Regent's men were sneaking weapons into the masquerade ball to kill the prince! Finally, Corinne and her friends have a chance to save Prince Louis from his evil cousin with a very clever plan. They wear disguises and sneak into the ball. Prince Louis names them royal musketeers. In the end, Corinne and her three friends ride horses saying, "All for One, and One for All!" and they are very happy.