Jack (Simon Pegg) is a children's author turned crime novelist whose detailed research into the lives of Victorian serial killers has turned him into a paranoid wreck, persecuted by the irrational fear of being murdered. When Jack is thrown a life-line by his long-suffering agent and a mysterious Hollywood executive takes a sudden and inexplicable interest in his script, what should be his 'big break' rapidly turns into his 'big breakdown', as Jack is forced to confront his worst demons; among them his love life, his laundry and the origin of all fear.