Instead of spending the summer with her grandmother on Cape Cod, ten-year-old Terrie Wright has been hauled off to England: her mother is studying at Kew Botanic Garden--where, somewhat unaccountably, Terrie is supposed to keep herself occupied day after day. As a plight, it's not exactly riveting--and even more out-of-the-way is the parallel fix of the haughy, oddly-garbed girl Terrie comes upon in a thicket: she's Princess Charlotte, granddaughter of George III, and because her parents (history's George IV and Queen Caroline) are estranged, she's virtually a prisoner at ""Grandpapa's"" Kew Castle. Once that's swallowed and digested, however, the growing rapport between Terrie and Charlotte has the usual time- and milieu-bridging attractions and does lead, eventually, to some outfight action. So that Charlotte can have a forbidden visit with her mother, Terrie cuts her long hair; the two exchange clothes; and Terrie, apprehensively playing princess, is almost found out and caught. Though it will be the last time the girls will see each other (Terrie, trying to make contact again, Finds herself firmly in the 20th century), ""each of them had helped the other when she needed it most."" The rest of the summer can be borne. Slight in its presumptions and rather obscure on the historical side, but pleasant in detailing the jeans-vs.-coronets implications.