A couple is running down the stairs of Montmartre. Sophie’s moving that way because she really wants to pee, her boyfriend is teasing her. They go into a toy shop to buy a present. She grabs a baby doll, he makes fun of her, reminding her that Gus is a boy. Sophie is now annoyed and they start arguing about the differences between girls and boys: the gender theory. Up to what point will they argue ? We end up in the middle of their debate, full of dishonesty and wit.
