Christopher Plummer

Genevieve digs up a huge bone in the garden that turns out to be a fossilized stegosaurus' hip bone. The girls are thrilled with the discovery until the Old House becomes a dig site and is invaded by hordes of paleontologists and equipment. Calm is briefly restored after Miss Clavel convinces Lord Cucuface to donate the bone to a museum.

The American child star Sugar Dimples becomes homesick when visiting Paris, and especially misses Halloween, which is not celebrated in France. At first Sugar Dimples does not appreciate the children's efforts to cheer her up, even when the girls and Pepito turn an abandoned castle into a haunted house.

Madeline convinces the young Prince of Monaco to remove his crown so he can spend an afternoon as an ordinary boy. But when the children return from the park, the priceless crown is missing. Using her superb detective skills, Madeline launches a citywide search that eventually implicates Pepito!

The newspaper sponsors a treasure hunt leading to a chest full of money. The clues lead the group to famous Paris landmarks, where the girls lose valuable time when they stop to help people in trouble (like a little boy whose sailboat has blown away). When they reach the treasure chest, someone else has arrived there first.

Madeline, Pepito and the girls take the famed Orient Express to Istanbul to compete in the International Spelling Bee. When a snake charmer on the train announces that his prize cobra is missing, Madeline and Pepito volunteer to search for the missing serpent (although the other girls refuse).

Lord Cucuface arrives at the Old House with a large chunk of prize-winning cheese (for fondue) and a new touring car. While Cucuface takes Miss Clavel for a calamitous driving lesson, the mice eat the cheese.

At the Old House - and all over the neighborhood - people's hats, gloves and scarves are missing. Madeline and Pepito work with Detective Moreau to find the perpetrators, then finally discover that the "thieves" are some altruistic magpies who are distributing the warm clothes to the homeless in the park.

The girls and Pepito visit Pepito's relatives' hacienda in Spain and encounter Pepito's cousins who are naughty and mischievous "bad hats", the way Pepito used to be (only worse!) The cousins terrorize everything in sight: various animals, the guests at their parents' fiesta, and even the girls. But after Madeline rescues a baby bull from their reaches, the Horrible Hats meet up with "El Enojado", an angry toro who teaches them a lesson.

It is Madeline's birthday, and Pepito and his father take her to the zoo while Miss Clavel and the girls get the house ready for a surprise birthday party. But when a mischievous monkey lets all the animals out of their cages, Madeline feels responsible and fails to make it home in time for the party. In the end, Miss Clavel relocates the festivities and Madeline gets to celebrate with her animal pals.

Madeline, Pepito and the girls visit Miss Clavel's aunt and nephew in their Alpine chalet. The trip is laden with adventure - from skiing and skating to an abominable snowman sighting. Later, when the group is trapped in the chalet by a terrifying avalanche, it is Madeline's spirit and ingenuity that saves the day.