Theodore’s world is shrinking. He cares for his grandfather, Émeril, whose dementia is increasingly tethered to a cryptic wartime past. Outside, a record-breaking heatwave has turned Quebec into a pressure cooker of domestic rage and inexplicable public violence.   In the shadow of this heat dome, the horseflies have arrived: large, predatory, and unnervingly persistent. To understand the infection taking hold of the province, Theodore must accompany Émeril back to Grosse Île, a secret military base where, in 1942, a young entomologist was conscripted to develop the perfect biological carrier.   Moving between the experimental horrors of the 1940s and a contemporary climate in crisis, Mireille Gagné’s novel is a visceral exploration of the predatory relationship between human violence and the natural world.