The Treason of Isengard continues the account of the creation of The Lord of the Rings started in the earlier volume, The Return of the Shadow. It traces the great expansion of the tale into new lands and new peoples south and east of the Misty Mountains: the emergence of Lothlórien, of Ents of the Riders of Rohan, and of Saruman the White in the fortress of Isengard. In brief outlines and pencilled drafts dashed down on scraps of paper are seen the first entry of Galadriel, the earliest ideas of the history of Gondor, and the original meeting of Aragorn and Éowyn, its significance destined to be wholly transformed. The book also contains a full account of the original map which was to be the basis of the emerging geography of Middle-earth; and an appendix examines the Runic alphabets, with illustrations of the forms and an analysis of the Runes used in the Book of Mazarbul found beside Balin's tomb in Moria.