An epidemic of yellow crawling brains threatens the lives of inhabitants in a reclusive Northern Quebec town.

1979. Donald Lavoie is a fearsome hitman who works under the orders of Claude Dubois, head of the Montreal South-West mob. Donald is tasked to take under his wing new recruit Serge Rivard, a hotheaded small-time crook who soon compromises him in a botched double murder. Donald avoids justice thanks to the Dubois clan's lawyers, but this is only a temporary setback for Detective Sergeant Roger Burns, who wants to convince Lavoie to become an informer.