A slow-starting British witch mystery, pieced together by the six Church Alley children (two of them the rector's children) from newspaper accounts, TV reports, a 19th-century canon's notebooks, letters, rumors, neighbors' accounts, and their own separate personal observations, written up or, in the case of a little brother too young to write, taped for the joint project. The mysterious business, stirred up when another historic church-cum-cemetery is moved to make way for an airport, brings a number of seemingly unrelated strangers to the children's remote village. These include African anthropologist Mr. Alabaster, M.A.; three old women the children come to recognize as Guardians, or good witches; the moppet of one of the three, an ancient wax mannequin who comes wanly and mechanically to life only in her ""mother's"" presence; the witch's real child, separated from her mother centuries before and now a ghostly wandering presence; and, at the center of it all, the grinnygog, a small stone figure found and brought home by a local resident but returned to the Guardians and Mr. Alabaster at a culminating Midsummer Festival where most of the villagers come out as hereditary witches. (As Mr. Alabaster predicts, they've all forgotten the magic in the morning, when the visitors have gone and the town has been swept clean of the old religion.) The patchwork structure of the story makes for jerky reading, impersonal and hard to get into. The African element, introduced perhaps to show the universality of the magic of creation, is sometimes awkwardly awry; and it will probably take a special attraction to Britain's Old Magic, which is in any case far more resonantly evoked in numerous other British juveniles, to keep American readers in tow.