Gaston Bernod is a Parisian bus driver. Honest, upright and hard-working, he is held in high esteem by his superiors. Gaston has always pampered "his" bus, going as far as to equip it with a fuel-saving device of his invention. Very close to his vehicle, he may have somewhat neglected his wife Paulette, who lets herself got round by the smooth words of Pierrot. The gigolo has indeed managed to persuade her to follow him to the Mont Saint-Michel, "a wonderful nest for their burgeoning love" as he says. The trouble is that Gaston, while driving his dear 84, catches sight of the car, and suddenly aware of his misfortune, sees red. He immediately sets off in pursuit of the culprits, involving his load of helpless passengers in the chase.

Gaston wants more than anything to marry the naive Simone. But where he is, there is Sidonie, a local singer romantically pursued by the police commissionaire.

After a novice nun learns of the sudden death of her parents, she leaves the convent to manage the family business and look after her teenage sister. Both of them fall prey to a womanizing mechanic with psychopathic tendencies.

Gilberte is a sixteen year old girl raised by her aunt and grandmother to be a demimondaine. But she's not ready for that yet, and spends her days in lessons and in teasing Mamita's old friend, the rich playboy Gaston LaChaille, and following his affairs from afar. But when Gaston throws off his latest mistress, it looks as if Gigi just might be ready to begin her destined career.