In Paris, if someone is picked up off the street suffering from amnesia or showing signs of delirium, they are taken to the city's emergency psychiatric unit, aka EPU, headed by Professor Mathias Bernardt who has less than 24 hours to decide whether to let patients return to normal life, check them into a hospital, or hand them over to the police. Preferring a human and thorough approach when treating the patients, he is constantly coming up against police captain Nathalie Fontaine, whose approach is more practical: to avoid cases piling up on her desk. Every day begins with a new patient, and every patient comes with a mystery Mathias and his team (Sophie, Julien and young intern Samy) must solve in a race against the clock to free up space for the next person brought in to the EPU.
