King Lear is universally acknowledged as one of Shakespeare's greatest tragic roles. Plummer has played the role under the direction of Sir Jonathan Miller (who, we discover, has directed it six times).

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.

To raise money to buy Miss Clavel a birthday present, Madeline starts a detective school. Meanwhile, Miss Clavel is receiving mysterious gifts of great value - jewels, a painting, etc. Inspector Moreau discovers they are stolen by the infamous cat burglar Le Chat and arrives to question Miss Clavel.

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, the girls, Pepito, and his three naughty cousins go on a field trip to Egypt. Nicole becomes terrified when they experience a series of mishaps - from getting locked in the museum to getting caught in a desert dust storm on camelback. Then the group gets lost in the pyramids and encounters a mummy who speaks to them in an echoey voice and curses them with bad luck!

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.

For their entry in the Science Exhibition, Madeline and the girls create a magnificent scale model of a hot air balloon. During the exhibition, Genevieve falls asleep in the balloon's basket and the balloon inadvertently takes off. With Genevieve floating over Paris, Madeline and Pepito enlist the aid of Professor Windbag, a hot air balloon "expert" who is more full of hot air than knowledge.

When the girls go for pony rides in the park, Madeline's pony, Gallop, (the smallest) does all sorts of fancy tricks and finally takes off, trotting across Paris! Soon they are discovered by Buffalo Ben, who invites them to appear in his touring Wild West Show.

Madeline, the girls, and Pepito prepare a disastrous meal for Lord Cucuface, who immediately enrolls them for cooking lessons at the famed Cordon Bleu. After various mishaps, the children finally get the hang of French cuisine, but Madeline fails to receive her diploma because she has given her creation to the hungry. In the end, Miss Clavel helps Madeline realize that the satisfaction of helping someone is more rewarding than any blue ribbon could...

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.