St Custard’s School for boys is in dire trouble! Someone has been stealing school funds to pay off shady gangsters. The school is now broke and may have to close. Young pupil Nigel Molesworth suspects one of the staff. He gets wind of a devious plan to nobble the school’s star football player, bet against St Custard’s to lose the National Schools’ Cup Final at Wembley, pocket the cash and flee the country. Determined to stop the culprit, rescue their star player and save the school, Molesworth embarks on a chaotic and hysterical race across 1950s London involving bank heists, wild animals, smog, the Kray twin gangsters, stunt-driving double-decker buses, Winston Churchill and the Queen!