A chilling tale about what happens when we mess with nature.

In 1942, a young entomologist, Thomas, is sent to a remote island to work on biological weapons for the Allied military. The scientists live like prisoners while they produce anthrax and look for the perfect virus carrier among the island's many insects.

Sixty years later, in the same region of Quebec, a heat wave unleashes swarms of horseflies while humans fall prey to strange flights of rage. Theodore is living a simple life, working double shifts and drinking to forget, when a horsefly bite stirs him from his apathy. He impulsively kidnaps his grandfather, whose dementia has him living in the past on Grosse Île.

The horseflies, meanwhile, know a few secrets...

Loosely based on historical fact, Horsefly is a terrifying tale about the ways in which we try to dominate nature, and how nature will, inevitably, wreak retribution upon us.