A writer discovers a set of notes in his notebook and sets off on a journey through the Paris of his past, in search of the woman he loved forty years previously. Set in the Montparnasse district of Paris, the author, Jean, retraces his nocturnal footsteps around the left bank during France's period of decolonisation during the 1960's. He tries to remember what brought him into contact with a gang that frequented the hotel Unic in the area. His quest through seedy cafes and cheap hotels becomes an enquiry into a woman, Dannie, whom Jean loved and who once tried to admit to a terrible crime. Over the course of several voyages between past and present, we meet various shady characters, and discover that Dannie may have killed "someone". As his memories overlap with the discovery of an old vice squad dossier, Jean reinvestigates the closed case of a crime where he could well be the last remaining witness.