A Plague Tale: Innocence

In November 1348, Amicia de Rune is a 15-year-old French noble living in Aquitaine during the Hundred Years' War between England and France. Her five-year-old brother, Hugo, has been ill since birth; their mother, Beatrice, an alchemist, has sheltered him in their estate while trying to devise a cure. While hunting with her father Robert in the forest, Amicia encounters an unusual substance on the ground, and her dog Lion is gruesomely consumed by an unseen entity. French Inquisition troops, led by Lord Nicholas, arrive at the de Rune estate in search of Hugo, executing Robert and slaughtering the family servants. Beatrice helps her children escape and instructs Amicia to take Hugo to a doctor named Laurentius, and is then seemingly killed.
Wanted by the Inquisition, the children find the local village and monastery overrun with hordes of rats spreading black plague. They eventually reach Laurentius's farm and find him severely ill with the plague. Laurentius implores Amicia to finish her mother's work seconds before the farm is overrun by rats; the siblings flee with Laurentius's apprentice, Lucas, to seek the Chateau d'Ombrage, which once belonged to the de Rune family. As they cross a battlefield patrolled by English soldiers, Lucas explains that Hugo's blood carries a supernatural evil called the Prima Macula, which has lain dormant within certain noble bloodlines since the Plague of Justinian. Beatrice and Laurentius had been trying to find an elixir that would mitigate Hugo's symptoms, while Vitalis Benevent, the Grand Inquisitor of France, seeks to harness Hugo's power so that the Inquisition can rule France. Hugo and Amicia are briefly captured by the English but escape with the help of sibling thieves Mélie and Arthur; Arthur is captured as the others escape to Chateau d'Ombrage.
Lucas needs a forbidden book called the Sanguinis Itinera to complete the elixir. Amicia retrieves the book with the help of a young blacksmith named Rodric, while Mélie rescues her brother. Back at the Chateau, Arthur reveals that Beatrice is still alive but imprisoned. Amicia insists they not tell Hugo, but he overhears the conversation. His anger appears to worsen his symptoms, prompting Amicia and Lucas to return to the de Rune estate and look for Beatrice's research. In a hidden laboratory, they complete the elixir and administer it to Hugo. Angry at his sister for not telling him the truth, Hugo runs away to the Inquisition in order to find Beatrice. Vitalis injects himself with Hugo's blood, but due to Lucas' elixir, he is unable to fully attain the power of the Macula.
Hugo escapes and finds Beatrice. Before their recapture, she reveals that the Macula gives him the power to control the rats. Vitalis threatens Beatrice's life to force Hugo's powers to fully awaken. Chateau d'Ombrage is then attacked by a swarm of rats guided by Hugo, still angry at Amicia. Nicholas, who is accompanying him, orders Hugo to kill Amicia, but she convinces her brother to reject the Inquisition. Nicholas kills Arthur, prompting the siblings to work together and battle Nicholas until the rats consume him. The children decide to confront Vitalis.
As they fight their way to Vitalis's cathedral, Rodric sacrifices himself to protect Hugo and Amicia. Vitalis awaits their arrival, having bred thousands of white rats that only he can control. Hugo ultimately overpowers Vitalis and Amicia kills him. Three days later, both the rats and the plague have disappeared and life begins to return to normal; many remain wary of Hugo and his power, including Mélie, who parts ways with the group. Amicia, Hugo, Lucas, and an ailing Beatrice leave in search of a new home.