On 21 June 1971, Richard Neville, James Anderson and Felix Dennis plead not guilty to charges of obscenity arising from the publication of their magazine 'Oz'. John Mortimer represents Anderson and Dennis, while Neville defends himself. Brian Leary is the barrister for the prosecution and the court is presided over by Judge Michael Argyle. Leary tells the jury that this is a case about whether issue 28 of 'Oz' tends to deprave and corrupt, while Mortimer claims that the case is really about the acceptance of dissent in society.

Vivian Berger gives evidence about the cartoon he designed for the magazine depicting Rupert Bear having sex with an old woman. He insists that it was only meant to be satirical and accurately reflects humour in many British schools. Detective Inspector Luff expresses the opinion that the magazine is a danger to society. Neville explains to the jury why he thinks that the magazine is a useful sounding board for those wishing to see change in society. He takes the stand and Leary takes him through several pages of 'Oz', unsuccessfully trying to make him admit that the publication panders to the desires of sexual deviants.

George Melly gives evidence in support of the magazine, saying that in his opinion much of the strong language used no longer has the ability to shock. He sees 'Oz' as part of a natural process of revolt among the young in society. Caroline Coon, an expert on teenage drug abuse, gives the opinion that 'Oz' serves a positive function in society by helping young people distinguish between soft and hard drugs.

During the second week of the trial, Anderson is cross-examined by Leary on whether the cartoons in the magazine are in fact obscene. Dr Michael Schofield expresses the opinion that much of the content of the magazine would be eminently suitable for school magazines and that too much emphasis has been placed on the cartoons as they are clearly only meant to be humorous and would normally be quickly forgotten.

During week three of the case, Dr Joseph Klein refuses to be drawn on whether the content is in fact pornographic, since neither Leary nor the judge is prepared to provide her with a definition of the word. Dr de Bono is asked if the content could be detrimental to readers. When he says that a sermon in church could be just as harmful to a person's sex life, the judge becomes agitated, insisting that the church be kept out of the case. In the fourth week of the trial the radio presenter John Peel describes the role that music has in sex, and explains why he went on the air to discuss his experiences with venereal disease. The artist Feliks Topolski speaks on the merit of the magazine's artwork, while the legal expert Dr Ronald Dworkin gives the opinion that 'Oz' is not obscene in legal terms.

During the fifth week, the comedian Marty Feldman is asked about the humour in the magazine, and upsets the judge and Leary by suggesting that the bible is far more obscene than an issue of 'Oz'. Felix Dennis is called to the stand and refuses to accept Leary's contention that the magazine caters to sexual perverts.

Leary and Mortimer give their closing speeches to the jury and are then followed by the judge, who makes it quite clear that he gives little or no weight to the expert testimony. When the jury asks for a definition of 'obscenity', he gives them the traditional definition from the dictionary. The jury finds the three men innocent of the conspiracy charges but does find them guilty of producing an obscene publication. Argyle insists that the men be kept in prison and subjected to psychiatric evaluation before sentencing. Neville is sent to jail for 15 months and a deportation order is drawn up. Anderson is sentenced to 12 months, while Dennis only receives a 9-month sentence for being less intelligent than the other two in the opinion of the judge. The convictions are quashed soon after on appeal on the grounds that the judge seriously misdirected the jury on the definition of 'obscenity' and by dismissing the expert testimony.