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.

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.

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 gets closer and closer to the serial killer when her best friend Lydia disappears. She is also sent to accompany Ketoff to leave France, as he has been asked to do so.