The bilingual "Hamilton School" is located on an island in southern England, with its Victorian buildings scattered through the park like the isles of an archipelago. The children are on vacation, but the empty school remains the haunt of its young owner, Alexandra Hamilton, a figure of fantasy to her four hundred students. She is holed up in her house, "defended" by an envious old principle, an overly-fond governess, and a nurse of easy virtue. "Defended" against whom, against what ? Michel, the only boy left on his own during the holidays, is taken in by Alexandra. And he tries to penetrate this mysterious defense...