A criminal produces an uncontrollable laughter to the population and Mortadelo and Filemón will have to stop him.

Paris, in the early 1960s. Jean-Louis Joubert is a serious but uptight stockbroker, married to Suzanne, a starchy class-conscious woman and father of two arrogant teenage boys, currently in a boarding school. The affluent man lives a steady yet boring life. At least until, due to fortuitous circumstances, Maria, the charming new maid at the service of Jean-Louis’ family, makes him discover the servants’ quarter on the sixth floor of the luxury building he owns and lives in. There live a crowd of lively Spanish maids who will help Jean-Louis to open to a new civilization and a new approach of life. In their company – and more precisely in the company of beautiful Maria – Jean-Louis will gradually become another man, a better man.

After losing his father, 10-year-old Carlos arrives at the Santa Lucia School, which shelters orphans of the Republican militia and politicians, and is taken in by the steely headmistress, Carmen, and the kindly professor, Casares. Soon after his arrival, Carlos has a run-in with the violent caretaker, Jacinto. Gradually, Carlos uncovers the secrets of the school, including the youthful ghost that wanders the grounds.