The Secret Diary of Adrian Mole Aged 13¾

The Mole family's neighbour Mr. Lucas is left by his wife, Mrs. Lucas. He and Adrian's mother Pauline have been having an affair, and they both leave to go to Sheffield, leaving Adrian and George, his father, on their own. Adrian meets old age pensioner Bert Baxter as part of the 'Good Samaritan' project at his school. Bert's filthy house and habits disgust Adrian, but they become friends. School bully Barry Kent begins demanding 'money for menaces' from Adrian, until Adrian's grandmother puts a stop to it by confronting the bully. Adrian takes a trip to Sheffield to see his mother and her lover, Mr. Lucas.

Struggling to come to terms with his mother's departure, Adrian wears red socks to school, which sees him sent home by the headmaster, Mr. Scruton. His furious father complains to Mr. Scruton, and Adrian's love interest Pandora Braithwaite organises a 'red sock protest' at the school, which brings her and Adrian together. Meanwhile, Adrian's friend Bert Baxter is taken to hospital with breathing difficulties.

Adrian wakes up unable to talk, and is diagnosed with tonsilitis. Meanwhile, an Asian family, the Singhs, move into the street which prompts some racist comments by Adrian's father. Bert Baxter leaves hospital and moves in temporarily with Adrian and George. The street celebrates the wedding of Prince Charles and Lady Diana Spencer with a street party. Adrian's sweetheart Pandora goes on holiday to Tunisia, and Adrian runs up an expensive phone bill making calls to her.

A school trip to the British Museum in London ends in disaster when the children go out of control and Barry Kent ends up arrested for theft. Adrian's phone calls to Pandora in Tunisia come back to haunt him when he receives the bill, which he hides from his father.

Adrian is admitted to hospital to have his tonsils removed, which brings his mother Pauline back to Leicester to see him. After spending a couple of days with George and Adrian, Pauline eventually returns to live with them. Adrian burns the phone bill in a bonfire on Bonfire Night, but he is forced to confess all when the phone is cut off. His furious parents make him pay the bill using his savings. Bert Baxter is now in an old people's home, where he meets a woman named Queenie whom he becomes engaged to.

It's Christmas Day in the Mole house, and Adrian annoys his parents by inviting Bert and Queenie over for the day. He receives a racing bike as a present. Having been made redundant, Adrian's father George gets a job with Manpower Services as a canal bank supervisor. Adrian breaks Pandora's heart by having a brief liaison with a classmate, Barbara Boyer.