The plot concerns a Montreal suburbanite who becomes obsessed with his award-winning lawn, which has become infested with a ground fungus. His neighbour across the street identifies the species as Amanita pestilens (not a real species, although Amanita is a real genus). The mushrooms prove impossible to eradicate, and the homeowner directs all his efforts to getting rid of them, to the exclusion of all else. His obsession very nearly destroys his life and leads to a deadly confrontation with his neighbour. A surprise ending, however, gives the viewer hope that the main character will see the error of his ways.