Lured into a magical mural by jaunty and mysterious Til Pleeryn whose art has breeched ""a thin spot in time,"" four children from Pawthany-On-Isle become Beyonders in the roughtly corresponding world of Pathania and find themselves pawns in a King-Council struggle where one side is as cruel and despotic as the other. The land is divided into mutually suspicious populations of lively Troges, plump Freelanders, timid Dalgurians and surly Hoonerans -- all plagued by carniverous trees (called Eebolyns) and variously transported by flying Ulfs or galloping Zylboks. The Beyonders of course come into some rough treatment in the natives' hands (and branches) but what with Carrie's pluck, Digby's music, Tonio's tale spinning and Leo's wits they manage to unite all forces against the rulers so that trust and brotherhood triumph in the end without a shot being fired. Adrienne Jones handles the devices of post-Tolkien fantasy cleverly -- Til's mural makes for a handy entry, the explanatory references to simultaneity and such are suitably offhand, and the victory by disarmament a neat updating of the good-over-evil outcome -- but they remain devices. There is a tired stamped out quality to the canvas filled with oddly-named creatures with their taglike traits, and even Til's occasional summoning rhymes -- more singsong than incantation -- betrays the mechanical nature of the whole creation.