Translation: As The Flies by Stuart Gilbert, 1946
Edition: Penguin, 1960
The Flies is a three act play telling the same story as Sophocles' Electra, but from a thoroughly twentieth century point of view. The familiar story concerns the return from exile and revenge by Orestes of the murder of his father, Agamemnon, by his mother and her lover (Clytemnestra and Aegisthus). For his murder of his mother, he faces punishment by the Furies (or Flies), who are the mythological guardians of the family.
In Sartre's version of the story, the kingdom of Argos has become a place of permanent penitence, where the people bewail their sins in an atmosphere full of flies, showing their corruption. The gods encourage this, realising the value to them of a nation that is truly "god-fearing". Zeus, transformed from his role in Greek myth as king of the gods and ruler of the sky, visits Argos as god of the dead and of flies. The purpose of his visit is to dissuade Orestes from his attack on Clytemnestra and Aegisthus.
Orestes is already not very keen on revenge; he feels that he has no reason to care for Argos (having been brought up in comfort in pleasant Athens); he feels nothing but disgust for what he sees of the lifestyle followed in Argos. It is only when he speaks to his sister, Electra, who is treated as a servant in the palace, and when Zeus tries to dissuade him, that he actually decides to go ahead.
The play is basically an attack on the idea of religion as Sartre saw it, and particularly on the idea of religious guilt. The gods are presented as immoral beings who delight in human suffering, which brings people back to belief in them. Orestes makes his choice without reference to the gods and begins the process by which rationality defeats and destroys religion. He uses his unbelief to defeat the Furies; he alone is the judge of his conduct.
Sartre has basically made religion out to be something easy to discredit, and proceeds to discredit it. It is all to easy, too glib to be at all convincing.