James McAvoy plays Detective Sergeant Bruce Robertson, a scheming, manipulative, misanthropic man who spends his time indulging in drugs, alcohol, sexually abusive relationships, and "the games" – cruel plots and systematic bullying of his coworkers and friends. While working on the murder case of a Japanese student, he starts coming unhinged, slowly losing his grip on reality and suffering from a series of increasingly severe hallucinations as he desperately tries to hold his life together.