Bruce Robertson is a Detective Sergeant in Edinburgh, Scotland who suffers from Borderline personality disorder. He is a scheming, manipulative, misanthropic bully who spends his free time indulging in drugs, alcohol, abusive sexual relationships, and “the games” — his euphemism for the vindictive plots he hatches to cause trouble for people he dislikes, including many of his colleagues. Robertson also delights in bullying and taking advantage of his mild-mannered friend Clifford Blades, a member of Robertson’s masonic lodge whose wife, Bunty, he repeatedly prank calls and asks for phone sex. The only people he shows any genuine warmth to are Mary and her young son, the widowed wife and child of a man whom Robertson tries and fails to resuscitate after he suffers a heart attack in the street.
As the story begins, Robertson’s main goal is to gain promotion to Detective Inspector, the path to which appears to open when he is assigned to oversee the investigation into the murder of a Japanese exchange student. He slowly loses his grip on reality as he works the case, however, suffering from a series of increasingly vivid hallucinations. It is ultimately revealed through dream-like exchanges with Dr. Rossi, his psychiatrist, that he is on medication for bipolar disorder and has repressed immense feelings of guilt over a childhood accident that led to the death of his younger brother. It also becomes clear that Carole, his wife, has left him and is denying him access to his daughter, Stacey, developments which sparked his desperate bid for promotion, played a part in his unusual displays of kindness toward Mary and her son, and have also led him to start cross-dressing as his wife when off duty in order to “keep her close” to him.
While wandering the streets on such an occasion, Robertson is kidnapped by a street gang led by the thuggish Gorman — who are responsible for the murder — and badly beaten. However, he manages to kill Gorman by throwing him through a window and is found by his colleagues. Robertson not only misses out on the promotion as a result of the events, but is in fact demoted to Constable and is reassigned to uniform, while rookie Ray Lennox is promoted to Detective Inspector. Afterwards, Blades receives a tape of Robertson apologising. Robertson then prepares to commit suicide by hanging himself, but is interrupted at the last moment by Mary and her son knocking at his front door. He then breaks the fourth wall and addresses the audience repeating his catchphrase — “Same rules apply” — and laughs as the chair slips from under him.