Louise, framed for murder, sees the only solution is to pose as her twin brother who has just been assigned a job as a detective. The discovery of the body of a woman modelling for artists leads her into the decadent world of high society.

Juggling at being both Gisele by night and Antoine by day, Louise is forced to trust a new person with her secret. While also wanting to uncover the killers of her father's friend, she is also compelled to find the killer of a young model.

When Fujita, an expatriate Japanese painter, reports the disappearance of his favorite model, Louise realizes that Céleste Dumont is not an isolated case.

Roman uncovers a secret. With a new ally, Louise discovers the place where the killer keeps his victims.

Louise wonders if the war could have turned her brother into a monster. Thanks to hypnosis, she learns that he had fallen madly in love with a nurse, Maria.