L'histoire débute en 1981, avec Bruno, Isabelle et Nicolas, qui ont tous les trois une vingtaine d'années. C'est aussi l'époque de la découverte du SIDA. Bruno aime Isabelle, la sœur de Nicolas, enceinte d'un autre homme. Nicolas aime secrètement Bruno.
In a prologue set in 1976, American epidemiologist Don Francis arrives in a village on the banks of the Ebola River in Zaire and discovers many of the residents and the doctor working with them have died from a mysterious illness later identified as Ebola hemorrhagic fever. It is his first exposure to such an epidemic, and the images of the dead he helps cremate will haunt him when he later becomes involved with HIV/AIDS research at the Centers for Disease Control and Prevention.