Plot
At the Roublès winemaking vineyard, the workers spray the fields with pesticides. When one of the workers becomes ill, complaining of a pain in his neck, his boss insists it's just a minor injury and tells him to go back to work.
Élizabeth is travelling by train to Roublès to live with Michel, her fiancé and the owner of the vineyard, and makes a friend with Brigitte, a woman on the train. Brigitte excuses herself to visit the restroom and doesn't return for a long time; then the vineyard worker comes aboard, encounters Brigitte, and a bit later joins Élizabeth in her compartment. In time, the man's neck suddenly grows an ulcer which starts oozing blood. Panicked, Élizabeth escapes him, stumbling upon Brigitte's corpse on the way.
Leaving the train, Élizabeth flees to a nearby village for help. A man named Pierre and his daughter Antoinette take her in, but react coldly to her tale. Élizabeth panics when she sees Pierre's arms disfigured by infection, but Antoinette holds her back, telling her to get upstairs to take a rest. When Élizabeth enters the bedroom and discovers a woman whose throat has been cut, Antoinette explains that the dead woman is her mother, and that her father killed her because he's become insane. Élizabeth and Antoinette try to leave the house, but Pierre, now featuring the same facial ulcers as the vineyard worker, catches them and rips open his daughter's blouse, revealing similar ulcers on her body. He kills Antoinette with a pitchfork, but Élizabeth flees and takes Pierre's car. When he gets in front of it and begs her to kill him, she runs him over and drives off.
Élizabeth travels further into the area to look for help and is approached by a man whose head is covered with ulcers and who is asking for help. When the pain from the infection makes him smash the car's window, the panicked Élizabeth shoots him with a revolver taken from the glove compartment. She comes across a blind girl named Lucy, who is searching for her caregiver, Lucas. While helping her, Élizabeth comes upon more bodies covered with the same strange ulcers strewn all over the village, while others are stumbling around like zombies, driven into murderous insanity by the infection. Élizabeth declines to tell Lucy, who runs off on her own and is killed and decapitated by Lucas, who has also been infected.
As the infected chase her, a blonde woman rescues Élizabeth. This woman has been trapped in a house for a few days, so she and Élizabeth try to get out and run, but the woman suddenly grabs Élizabeth and leaves her to the infected. Two men, Paul and Lucien, show up and start killing the infected. They encounter the blonde, who convinces them that she is not infected by briefly disrobing, and they tell her to wait by their truck. Escaping her assailants, Élizabeth reaches the truck, where she and the woman get into a fight. Élizabeth clubs her with a torch, revealing previously hidden infection boils on the woman's face. The woman then tosses the torch into an open dynamite crate on the truck, blowing the car up and killing her.
While Élizabeth, Paul and Lucien leave the village on foot, they begin to deduce that the infestation happened just after a wine festival on the Sunday before. Élizabeth suggests seeking out her fiancé for answers, and so the three proceed to the vineyard. Finding it apparently abandoned, Paul and Lucien sit down for a meal after learning from a phone call that the authorities are aware of the infection. Restless, Élizabeth searches the grounds and finds Michel, also infected but still lucid. He reveals that he invented the pesticide which tainted the wine that started this baleful infection, which spread so quickly because he had illegally employed immigrants as cheap labor, which prevented him from notifying the police.
Despite Michel's urgings that she stay away, Élizabeth embraces him. When Paul comes looking for her and discovers the two, Michel, unwilling to become insane, leaps at Paul, compelling the latter to shoot him. Now apparently infected herself, Élizabeth picks up Paul's gun and shoots him, then ambushes and kills Lucien when he comes looking for them. The film ends with Élizabeth allowing Michel's blood to drip on her face from the loft above.
