John Pielmeier’s play Agnes of God begins in tragic circumstances, with the discovery by nuns at a Canadian convent of a newborn baby, choked to death by an umbilical cord and concealed inside a trashcan. Agnes, the baby’s mother, is accused of its murder, and a psychiatrist, Dr. Martha Livingstone, is sent by the court to examine her. The play’s cast consists of three characters: Martha, Agnes, and Miriam, the mother superior, who also happens to be Agnes’s aunt. In addition to this, figures such as Agnes’s overbearing and abusive mother; her closest friend at the convent, Sister Marie-Paul; and the judge overseeing the case play a role in shaping the plot.

Throughout the play, Martha employs a variety of approaches in order to get the truth out of Agnes, presenting a front which is by turns antagonistic and nurturing, skeptical and open-minded. The greatest challenge she faces in her efforts is ascertaining how far Agnes’s capacity for rational thought has been compromised by her faith. She also faces suspicion from the other nuns at the convent, who feel that her atheism will lead her to treat Agnes unfairly, not to mention active opposition from Miriam, who is convinced of her niece’s innocence, repeatedly asserting that Agnes lacked both the knowledge and the opportunity to have conceived a child. Miriam initially seems to accept Agnes’s claim that hers was a virgin birth, and moreover that she had no recollection of being pregnant. She admits under hypnosis, however, that she was aware of Agnes’s pregnancy, though she stringently denies having killed the baby. Also under hypnosis, Agnes herself comes to admit that she lied on this latter point.

Martha spends time exploring the convent, locating a barn that she suspects might have been the venue in which Agnes met the person with whom she had her baby. However, this barn is proved a red herring by Agnes’s subsequent admission that she was introduced to “Him” by Marie-Paul in a bell tower that the pair used to frequent. The play’s climax comes with Agnes’s admission that she killed her baby, believing it to be “a mistake,” an accusation that she had on numerous occasions been made to bear by her mother. Having been found not guilty by the court due to her insanity, Agnes is permitted to remain at the convent, under the close care of her sisters and her aunt.