Morgane's pregnancy disrupts her daily life, but she still has to return to work. Alexandra Collet, 42, a stay-at-home mom deeply connected to her hearing-impaired son, is found dead by her husband. The investigation takes a different turn when detectives uncover that the victim led a double life as a drug dealer.

At the hospital for her ultrasound appointment, Morgane is called to a crime scene: Dr. Bubé has been murdered with a fire extinguisher in his office. The crime scene is chilling, given the violence depicted in the images on site. The investigation takes a strange turn when the team discovers that anti-speciesist activists are involved. Morgane will have to unravel the mystery of this murder alongside Karadec, who is preparing to leave the force, and Commander Prigent, her successor. A task that matches her abilities but appears much more complicated than it seems.

As her children compel her to contact the other potential fathers of her child, Morgane is called to a new investigation: Antoine Broussin, an 85-year-old crime novelist, is found dead in a secret room in his home. The investigation becomes complicated when Marie Besnard, an acquaintance from Morgane's time in prison, becomes the prime suspect.

Tristan Delvallée, a procurement officer for a maintenance company, is found stabbed. To their surprise, the team discovers that the victim was also a hacker. Morgane will have to solve this case. The problem is, her case is linked to Karadec's. The duo will be forced to collaborate once again, despite their recent tensions.