Madeline paints a magnificent picture and accidentally leaves it at the Louvre, where it is mistaken for a masterpiece and hung next to the Mona Lisa, upstaging DaVinci's creation. Madeline tries to get the painting back, but one believes that she is the anonymous artist. In the end she finds she must use her feisty individuality to prove herself to the authorities.
After being evicted from the opera for barking along with her favorite arias, Genevieve is dog napped by an impresario who sets her up at a dinner theatre. When Madeline finally catches up with her talented canine, Genevieve, now a star is reluctant to go home because she is still embarrassed about the incident at the opera. It is up to Madeline to convince Genevieve how much she is missed at the Old House.
The girls get a chance to perform with a famed ballet master who thinks Madeline is too small to succeed. Madeline's insecurity (and Pepito's teasing) keeps getting in the way of her performance until she is given a pep talk - and a pair of toe shoes - by an accomplished prima ballerina, who convinces Madeline that hard work and courage will help her excel.
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 ever be.
When Madeline and the girls visit a toy factory, Madeline is accidentally boxed as a "doll" and sold to a handicapped girl. The ailing child considers Madeline her only friend and is devastated when Madeline reveals her true identity and has to go home. But things turn around the next day when the little girl discovers she now has twelve real live friends.
The Old House, sorely in need of repair, is condemned and the girls are forced to move to a small apartment where their snooty neighbors hate kids and dogs. But just before the wrecking ball destroys their beloved abode, Madeline enlists the aid of the ladies of the Historical Society, who help get the Old House renovated to perfection.
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.