Luc Gavardine (usually called by his surname) begins the narration by saying he can't get into his big appartment (which doesn't have a part in the story, apart from his not being able to enter it) because Anne (whom he's at the time living with) isn't there to let him in, and he's lost his briefcase in which he carries he key. A lost key also appears at the end of the novel, although he finds it, as if he's unlocking the door to a new life, or maybe not.
Gavardine spends the night in a hotel (this is written before mobile phones became ubiquitous), and then goes to the florist shop where Anne works, to be told that she didn't go to his big appartment that night. Instead of asking her why, is the relationship therefore finished, and if so can he have his key back, Gavardine just goes away, buys a new briefcase and goes to the swimming baths to see an old female friend. But when he gets there his friend loses importance and it's love at first sight for him when he sees Flore (nothing to do with florists), who is heavily pregant, walks with her from the baths, and even arranges to go to the Corrèze on the train with her, where she's going to see her brother.
'Why?' and 'What if...?' don't necessarily count for much in Oster's world, and life-changing decisions are, well, just part of the normal course of events. Not that Gavardine has anything to lose by giving into a whim, as he seems to accept that he's lost his girlfriend Anne, doesn't have a job, so why not join Flore to meet her brother, even though he doesn't know if the father of her future child is still around?
As it happens, Flore's brother Jean, who runs a bar and an adjacent museum, welcomes Jean as a brother-in-law (Flore having been hastened to hospital to give birth to a baby called Maude) and even offers him a job of sorts as museum guide. Jean doesn't seem to be too much concerned that Luc (they're now on 'tu' terms) has only met Flore two days before and obviously isn't the father, and as for Flore, well, she doesn't love Luc but maybe things will work out all right.
Strange things happen to male protagonists in Christian Oster's books, and it's usually women who cause them: don't ask too many questions, just enjoy his highly original, amusing, and very engaging novels.
Christian Oster: Dans le train
Christian Oster: Une femme de Ménage | Cleaning Woman
Christian Oster: Rouler
Christian Oster: Le Cœur du problème
Christian Oster: En ville