After fifteen years in exile, Orestes returns to his hometown of Argos to discover that his mother (Clytemnestra) and her lover (Aegisthus) have killed his father, King Agamemnon. The usurpers hold the people in bondage and misery through fear, and Orestes' sister, Electra, has been reduced to servitude. What is next?

Using ancient mythological material as a foundation, Sartre skillfully directs our attention to important themes for personal and societal well-being. First and foremost, the theme of freedom. Sartre argues that "man is condemned to be free." No one has power over us unless we choose to give them that power. Freedom is a gift, but also a burden; it comes with responsibility.

The theme of choice. Since existentialists believe in radical personal freedom, everything is a matter of choice. We choose our values, we choose our identity, and we even choose whether to live or not. By constantly creating and recreating ourselves, man must choose a set of values through action. It's important to note that action, not thoughts, beliefs, or aspirations, constitutes this choice. By choosing a specific value (such as honesty, freedom, repentance, etc.), we create it. For Sartre, avoiding choice means escaping personal freedom or self-deception.

The theme of guilt. Guilt is imposed by the rulers of the kingdom—Aegisthus and Jupiter. They use guilt as a tool to suppress their subjects. As long as the population is occupied with repentance and regret, they are distant from their personal freedom. The people of Argos have forgotten that it is up to them to choose a system of values and decide what is right and what is not. Instead of making their own choices, they allow an external force to impose a system of morality upon them.

"Flies" (similar to the fundamental idea of existentialism) aims to convey to people that the power of kings and gods is based solely on the fact that people do not know they are actually free. They are free to make their own decisions, to walk their own path, instead of blaming an authority figure for everything and thus shifting responsibility away from themselves.