Having been struck from the medical register, Alexandre now treats criminals. Anonymous and methodical, he rules over this underground world. Until the day Zacharie appears, bearing a strange bite: "When night falls, I will transform… and kill you." Initial tests do indeed reveal troubling mutations in his body. Confronted with something he could never have imagined, Alexandre will discover that in addition to his own survival, the future of medicine and the entire human species is at stake.