Alyson surprises Arben and Nathalie in the middle of a discussion and thinks she has understood the reasons for her departure; Hugo worries about Igor, who hasn't come to work; Chloé faces reclassification, but the young woman copes.
Patients poisoned by carbon monoxide are admitted to the emergency room. Arriving with them as a rescuer, Arben carefully avoids his former colleagues; Alyson fights to get her patient into a hyperbaric chamber.
The discovery of an inanimate patient shocks the entire team and triggers an internal investigation; Doctor Brun discovers how chaotic the management of patients is.
When a patient suddenly dies, the team ends up in shock. Hospital manager Nathalie Ferrand decides to send Arben back to the pathology department to examine the body.
Chloé wakes up but her behaviour is causing concern among those around her, especially Simoni. The manager reveals that everyone will be questioned by the legal department.
After the incident with Mrs Marciano, Brun reorganises the ER; Igor tries to make a good impression, but shows signs of fatigue; Hugo has problems with his mother again.
After Chloé has a heart attack, Professor Wagner takes care of her. Alyson and Hugo make several important discoveries at Chloé's home and Arben feels guilty for not suspecting anything.
Hugo discovers that Madame Marciano was Igor's patient and must inform Olivier Brun. He begins to worry about his friend who shows signs of mental overload.