In a high-rise luxury apartment complex on the outskirts of Montreal, the residents' tranquil lives are upended when a scientist's experimental parasitic organism designed to replace human organs goes horribly awry. The parasite turns its hosts into aggressively sexual beings, propagating rapidly through intimate contact. The twisted experiment begins with Dr. Emil Hobbes, who implants the parasite in a young woman named Annabelle. When Dr. Roger St. Luc, the building’s primary physician, discovers Annabelle dead in her apartment, he uncovers Hobbes’ grim secret and the horrifying nature of the parasite.

As residents unknowingly become carriers of the organism, paranoia and chaos spread throughout the building. Dr. St. Luc, assisted by his nurse Forsythe, becomes embroiled in a desperate struggle to contain the outbreak and discover a cure before the community is completely consumed. Amidst escalating violence and rising hysteria, communication breakdowns and the deteriorating social conditions make containment nearly impossible, leading to a relentless and ominous trajectory of infection and madness within the once-peaceful residential tower.