The Royal Book of Oz (1921) is the fifteenth in the series of Oz books, and the first to be written after L. Frank Baum's death. Although Baum was credited as the author, it was written entirely by Ruth Plumly Thompson. Beginning in the 1980s, some editions have correctly credited Thompson, although the cover of the 2001 edition by Dover Publications credits only Baum. The Scarecrow is upset when Professor Woggle-bug tells him that he has no family, so he goes back to the corn-field where Dorothy Gale found him to trace his "roots." When he fails to return, Dorothy and the Cowardly Lion set out to search for him. They meet an elderly knight, Sir Hokus of Pokes. They also meet the Doubtful Dromedary and the Comfortable Camel. Together, they have several curious adventures while searching for the Scarecrow.