The Girardis have moved to the small town of Arcadia from the big city after patriarch Will gets a job as chief of police. Middle child Joan isn't happy, and her family, consisting of science nerd Luke, paralyzed former jock Kevin, and their perpetually flustered mother Helen, isn't helping. Then, Joan finds herself speaking to God, in the form of various people who give her assignments to help those around her. As her friendship with the zoned out avant garde sculptor Adam Rove and androgynous rebel Grace develops, Joan keeps following God's assignments, never sure if she's really just going crazy.

Show creator Barbara Hall wrote a list of guidelines for the writers, which she called "The Ten Commandments of Joan of Arcadia". These "commandments" are: - 1. God cannot directly intervene. - 2. Good and evil exist. - 3. God can never identify one religion as being right. - 4. The job of every human being is to fulfill his or her true nature. - 5. Everyone is allowed to say "no" to God, including Joan. - 6. God is not bound by time. This is a human concept. - 7. God is not a person and does not possess a human personality. - 8. God talks to everyone all the time in different ways. - 9. God's plan is what is good for us, not what is good for him. - 10. God's purpose for talking to Joan, and everyone, is to get her (us) to recognize the interconnectedness of all things - i.e., you cannot hurt a person without hurting yourself; all of your actions have consequences; God can be found in the smallest actions; God expects us to learn and grow from all our experiences. However, the exact nature of God is a mystery, and the mystery can never be solved.

Grace Polk:
It's the one advantage to being universally despised: you get to say whatever you want.

Performed by Joan Osborne
(Title Song)