Agnes of God is both a mystery and a psychological exploration of religious faith. When the play opens, the young nun, Agnes, is bleeding, prompting the viewer to wonder why. The newborn baby’s corpse is soon found in the trashcan in her room, inevitably leading to the assumption that she killed the baby. It seems likely that she has just given birth, but she admits to nothing. Thus questions immediately arise regarding whether she is the mother and the killer. Assuming that one of the convent’s nuns is the mother, the subsequent, related question of the father’s paternity also quickly arises.
Two other main characters besides Agnes are presented as foils: Martha, the psychologist interviewing Agnes, and Miriam, the convent’s Mother Superior. Martha’s inquiry drives the mystery-solving side of the play and provides some insights into the young woman’s thoughts and actions. Her interactions with Miriam help increase the tension because at first Miriam insists she does not believe Agnes is capable of such actions.
Agnes continues to insist that she did not have sex and thus could not have had a baby. However, the information provided strongly suggests that she is the baby’s mother, which she does later admit. This raises another mystery, if she is laying claim to a virgin birth.
The climax comes when Agnes also admits that she strangled the newborn whom she had just delivered alone. The resolution involves the characters’ coming to terms with her sins and crimes, and she is ultimately allowed to stay in the convent.