Grégoire Lecomte, the unlucky actor anxious to find a "real job", goes to take a screen test for a role of a killer, but gets to mafiosi by mistake. He takes their don for a producer, and they mistake him for a hitman with whom they had an appointment. Deluded Lecomte signs contract with them. He is supposed to kill gun dealer Otto Krampe at his birthday party in Saint-Tropez by piercing him with a cap of the umbrella with a built-in syringe with potassium cyanide. Lecomte is not aware that it has to be a real murder.
The story centers around a graduating class of "less-gifted" students in a private Versailles high school. Only a miracle has brought the students this far along, and after a practical joke misfires and the whole school is dynamited, the students are in deep trouble. They have to present themselves in court for their punishment and it could not be worse: If they don't pass their high-school graduation exams, they go to prison!