Freddie is an inept bank clerk with no future. His only hobby is collecting butterflies, which gives him a feeling of power and control that is otherwise totally missing from his life. He comes into a large sum of money and buys himself a country house. Still unable to make himself at ease socially, he starts to plan on acquiring a girlfriend - in the same manner as he collects butterflies. He prepares the cellar of the house to be a collecting jar and stalks his victim over several days.

• Thriller