An epidemic looms. Anne-Marie Leclerc, director of the Emergency Public Health Laboratory, must deal with an outbreak, an overzealous cabinet minister, and a media storm. To top it off, she discovers that her husband has been deceiving her. All this is trivial compared to what’s in store...

The disease continues to spread silently. For now, Anne-Marie has other worries. She sets out to prove to the Minister that her lab is effective. She’s still hesitant to confront Marc. Françoise organizes a celebration for Xavier. It’s a small gathering – with immense consequences.

Nelli tells Anne-Marie that a strange illness is affecting people she’s close to. Anne-Marie initiates an investigation into the deaths of the two homeless people. The young girl infected by Nelli’s cousin risks infecting others. In the lab, the arrival of a new staffer affects Anne-Marie’s work.

The dead can’t talk. Anne-Marie needs to know if people close to the victims are suffering from the disease. The clock is ticking. The lab team does all it can to break the chain of transmission and discover the nature of the virus.

Unaware that the epidemic is developing a second hot-spot, Anne-Marie focuses her energy on finding medication that will help patients. Will she go as far as breaking the law? Françoise is now in contact with Marcellin, a friend of Xavier’s who’s suffering from the same “flu.”

Cases of COVA are multiplying; enforced home quarantines number in the hundreds. Anne-Marie redoubles her efforts to contain the epidemic and limit deaths. Confined to her home, Geneviève hides her symptoms. She has one wish – to be near her hospitalized son – even if that means breaking the rules.

Anne-Marie combats the misinformation prompting irrational behavior. The minister no longer has faith in her and wants to be directly involved in the experimental treatment. At the lab, Nelli follows up a new lead in the investigation. Will she find the source of the virus?

The 200th COVA death is about to be announced. How can public panic be minimized? Montrealers are fleeing the city and ignoring symptoms. Anne-Marie needs a new strategy.

A drop in the number of new cases heralds the end of the epidemic. Will there be a second wave? Anne-Marie is suddenly confronted with several cases of sick people who have had no contact with infected individuals. The team works to solve the puzzle. Sabrina and Juliette sell their first ferret.

Two days before the official announcement that the epidemic is over, the infection of two little girls brings Anne-Marie back to square one. The epidemiological investigation resumes, but the girls are uncooperative. Will Nelli get them to talk and prevent COVA from claiming more victims?