During their Spring Break school vacation, twin sisters Melanie and Allyson Porter travel to Paris to visit their Grandpa Edward, the U.S. Ambassador to France. Expecting a great time with their grandfather, they instead end up with his no-nonsense assistant, Jeremy Bluff, chaperoning them. While there, they befriend Brigitte, a beautiful French fashion model (with whom they later set Jeremy up on a date), and fall for two charming French boys named Jean and Michel. The girls find various ways to ditch Jeremy, so they can spend time cruising around the city on mopeds with the boys.
Absorbing all the sights and sounds of Paris, Melanie and Allison end up in police custody, along with Jean and Michel, for trespassing on private property. To their dismay, the girls are hastily forbidden by Grandpa Edward to see the boys again. So they challenge the French Foreign Minister, Monsieur De Beauvoir, at a banquet, and manage to convince him to accept an important proposal that was established by their grandfather, concerning clean drinking water for the Embassy. This puts Melanie and Allison back in Grandpa Edward's good graces, and he allows them to once again see Jean and Michel – even allowing all four of them to attend a dance together.
Finally, when the time comes for the girls to return home, Grandpa Edward decides to take a much-needed break from his ambassadorial duties, and accompany them; the intention being to spend time with his family (who he hasn't seen for a long time), back in the United States.