The Sword in the Tree is a historical fiction novel set in an imagined version of medieval England. While the story is a fantasy, Bulla’s setting and characters exemplify the real feudal structure of England in the Middle Ages. In the story, the country is a monarchy ruled by a king, who assigns the country’s regions to lords and other nobility to rule over. Lord and Lady Weldon belong to this aristocratic class and preside over Weldon Castle. Shepherds like Magnus belong to the rural peasant class, who live and work under the domain of a particular Lord. Like most real medieval societies, the social world of the novel is strictly hierarchical, which is why Magnus is surprised to meet Shan and Lady Weldon and discover that they are in need of his help. 

The Middle Ages is also noted for its cult of chivalry, an aristocratic code of behavior and values that was supposed to shape the conduct of knights and other members of the nobility. According to the tenets of chivalry, a knight was supposed to behave with honor and integrity, protecting the weak and fighting against the injustices of the powerful.