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.
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.
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.
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.
Hugo finds Igor, unconscious, in the hyperbaric chamber. The entire hospital team is in shock and the question arises whether it is an accident or a suicide attempt.