The play is set in Brussels, where Suzanne Beulemans, daughter of a wealthy brewer, is promised in marriage to Séraphin Meulemeester, son of a rival brewer. Both the young man and his father appear particularly motivated by the young bride's dowry. But Séraphin has a rival in the form of Albert Delpierre, a young Parisian intern at the Beulemans brewery, who is secretly in love with the young woman.
Rosette is young and charming but she is crippled so she cannot make the most of her life. Which upsets Jules Petitpas, a single inventor, her eccentric but kind-hearted neighbor. Jules pledges to help her by creating a potion that will cure her. Unfortunately he dies before being able to achieve his aim. But a promise is a promise, and the good man comes back to the land of the living as an ... ectoplasm! And he manages to involve a whole tribe of ghosts to assist him in the noble task of saving the young lady. All is well that ends well.
Pouske runs the "Le Bienvenu" café with his wife Antoinette and daughter Jeanne. On the market square, the fairgrounds are setting up their rides and the neighborhood is getting ready to party. But Jeanne is about to fall in love with a sweetheart who has come from who knows where to cause trouble.
