Christian Janvier has been working on the Forgotten Girls case for 15 years. Close to the families of the six missing girls, he refuses to give up on the investigation. Assisted by Olivier Ducourt, a young gendarme, he uncovers the disappearance of a seventh young woman, Sylvie Trebourg.
The body of Sylvie Trebourg has been found in the garden of Roland Guerrand. Under interrogation, he admits to the murders of the other six girls, but when the police search the alleged burial place, they find nothing. If he did kill Sylvie, it seems that Roland Guerrand is not the one Janvier has been looking for all these years.
Christian Janvier’s memory problems are increasing. As he moves forward in his investigation, he believes that if Roland Guerrand really is guilty of the last crime, he must know the true identity of the assassin. At the crime reconstruction, Janvier loses control and tries to force Guerrand to reveal the real killer’s name, but to no avail.
Guerrand is killed by Sylvie’s father. Destabilised by the disappearance of the killer, Janvier doesn’t know where to look for the truth. Accompanied by Ducourt, he looks back at Guerrand’s past and discovers the very first victim from 23 years ago. A new line of enquiry to lead him to the assassin.
Janvier and Ducourt delve into the past of Emilie Fontrave, the killer’s first victim. In search of a clue or a trace of DNA, they request that the young woman’s body be exhumed. As Janvier immerses himself in the documents about the murdered girls, he also realises they are all connected by their love of music.
Clara has disappeared – a new victim of the killer that Christian Janvier has been hunting for more than fifteen years. Janvier and Ducourt must act quickly if they are to save the girl. But as the investigation progresses, Janvier’s illness is amplified: after all, what was he doing yesterday when Clara disappeared?