The central theme in this book, which was so popular that it was translated into several European languages and sent to occupied countries during the Second World War, is that of resistance against an occupied force, and how the resistance organically sprang up against the invading force. The occupation is shown to be the making of several characters, becoming the catalyst that some of them need to be able to find their inner hero and become involved in the resistance work against the invading force. The character of Mayor Orden, for example, moves from being something of a figure of fun at the beginning of the novel to a major leader of his people. Note how the following quote relates to the theme of resistance and uprising:
I am a little man and this is a little town, but there must be a spark in little men that can burst into flame.
The theme of this text therefore is based on the "spark" that can cause "little men" to put aside their diminutive stature and "burst into flame," causing men who are normally diffident and unassuming to be able to stand up for their own freedom and to resist occupation. Another quote, "The flies have conquered the flypaper," is an ironic comment on the power of the many and the potential that there is in resistance.