What was going on in the mind of schizophrenic Mary when, five years ago, she killed her mother? Was she mad - and if so, by whose definition? This film examination of madness, and what we mean by it, centres on the series of interviews conducted with Mary by psychiatrist Dr Pamela Taylor. Actress Diana Rayworth re-enacts events to aid the investigation. The film also looks at the Yorkshire Ripper case, and at the dilemma faced by psychiatric experts whose diagnosis of madness may be crucial in a criminal case