English twins, Anne and Patrick, are enchanted with the beautiful library in their host's home outside London. They are especially intrigued by the stained glass window featuring a graceful unicorn. The horror of accidentally shattering this prized window is somewhat relieved when the twins find themselves in a strange fairy land bordered by four magnificent castles and inhabited by a throng of gracious and charitable hosts. Once inside the marvelous halls of Armorse the children hear the legend of the unicorn and Anne is informed that only a maiden from the Outside like herself can retrieve the gentle creature from exite in No Man's Land. The wonderful sights and adventures inside this charming world are climaxed by Anne's good deed which is later celebrated by a beautiful festival held in her honor. Did it all happen or was it a dream? Neither the twins nor the reader will ever know -- but the unicorn window pane in in perfect condition when they awake in the library. A smooth, gentle trip into fantasy, filled with whimsey and imagination.