The Door in the Wall is primarily a story of heroic bravery and surmounting challenges against a highly chaotic historical backdrop: medieval England. In the background of Robin's own personal struggles is the epidemic of the Black Plague, a disease that wiped out hundreds of millions of Europeans in a span of just a few years. The Black Death (as it is also known) features prominently in the plot of the story, as it is the catalyst for Robin being taken to the monastery by Brother Luke after all of his family servants come down with the sickness and leave him alone. Throughout the months in which the story unfolds, there is also a waxing and waning of the plague, and author Marguerite de Angeli uses the abatement of the disease to symbolize a new time of hope for the people of England, including Robin and the royal order.
Still, even with a reduction of the plague, the disease had already made its mark on British society, transforming all aspects of social and cultural life, especially in cities like London. It is noted in Norman F. Cantor's book In the Wake of the Plague that it was in England where the disease wrought the most devastation, especially in the 15th century. The scholar Shona Kelly Wray notes that societies had different ways of tackling the disease, and it was frequently the churches and other ecclesiastical organizations that led the relief effort: caring for the sick and leading sermons to beg forgiveness for what they considered to be the wrath of God. These attempts to counteract the crisis are portrayed in The Door in the Wall: we see how Brother Luke and the other monks of St. Mark's take it upon themselves to deal with the many sick people flooding the monastery. In this way, the church served as a kind of refuge for the needy to receive blessings in times of great hardship.
The plague and the havoc it caused shook the English people to their core, testing their religious faith yet also bringing the society closer together as poor peasants and noblemen alike were not immune to the effects of the disease. By spending time among the sick at St. Mark's, Robin, the son of noblepeople, is reacquainted with a sense of humility and gratitude for life, helping him to develop the selflessness required to save the Lindsay castle.
