Moving from Kansas to a hexagonal house along the Croton, New York aqueduct with her mathematician father (a college teacher who talks more like a pompous kid, calling his family a set and ""calculating"" what to do next) and her dental hygienist mother (who measures the world against her ideal of freshly scrubbed teeth), Aggie Moon wonders why townspeople avoid the ""hex house"" and warn her against using the telescope she finds there. While her parents are working, Aggie makes friends with two orphan boys who accidentally break her bicycle and with Sister Bright who comes to tea and advises her to confide in her parents about the boys and the bike. When Aggie reports a fire and near drowning she observes through the telescope, the police hang up on her, but later they come to apologize and, as Mr. Moon puts it, supply ""the unknowns in the equation"" of Hex House. But the disclosure that the last kid in the Moon's new home had been a voyeur who had turned in a false murder report is hardly enough to explain all the intimations of evil and magic or to make the adventure -- despite the house's special physical dimensions -- more than a standard prefab story.