Claire and Harold invite their new neighbors for drinks to get acquainted and thank them for their help. As the evening unfolds, the conversation becomes strained and strange things start to happen. Claire and Harold are left with many unanswered questions.

Soon after Claire and Harold move into their new Parisian apartment, strange things start to open. Their new neighbors explain that their new home may have been the scene of a murder. Claire believes it, but Harold remains skeptical. Will they be able to solve this mystery?

In part one of "Le Jour où tout a basculé: Nos bébés ont été échangés" (The Day When Everything Changed: Our Babies Were Switched at Birth), a family is in turmoil. Frédéric is very jealous of his wife Anne-Sophie and accuses her of having an affair with an old flame. Although all the evidence seems plausible, is there another explanation?

In this episode of "Le Jour où tout a basculé" (The Day Everything Turned Upside Down), Sybille, a bored and lonely housewife, has developed the peculiar habit of spying on her neighbors across the street, much to her husband's dismay.