Surprisingly, there is no demand for the services of William Graham and his fellow Knights of the Square Table (wrongs righted, sixpence or one shilling). William turns his attention to his elder brother, who hasn't married movie star Hy Hazell, or even introduced himself. Eventually he concludes it's because of the post-war housing shortage. The Knights of the Square Table, therefore, decide to haunt the biggest house in town; once the owner has fled, William's brother and his bride can move in to enjoy connubial bliss. But, alas! Tramp A. E. Matthews knows how to do this and more. He, however, insists on a two-bob initiation, which the boys haven't got. So they have to haunt the place on their own, just as ur thieves are using the place to hide their loot.
With father Garry Marsh on the boil, William has a hard time keeping out of trouble.in this harmless but amusing screen version of one of Richmal Crompton's numerous 'Just William' stories.