Audrey Hepburn stars in a based-on-true story of a woman who joins the religious outfit in order to pursue her dreams of helping people in Africa. Her problem lies in the fact that she's not allowed to have "dreams" or "aspirations". That's the constant struggle with Sister Luke. It's not lust or order or possessions. But she's an accomplished scientist and nurse and she struggles with her pride in those accomplishments. And her desire to put her scientific mind to work. This all goes against the rule of order of Nunnery Row.
If this was the only thing that was ever discussed in this movie - her praying and biting her frustrated lip - it would be a boring movie. It succeeds because the scenarios that the Sister is placed in find unique and challenging ways in showing her struggle. Not with faith in God; but certainly in the inhumane rites of being a nun.
The efforts in starting her studies, her time working in a sanitarium, her time in the congo, war in Europe. In all of these settings, she follows her head and her heart. What others would call God's voice, she is only taught to know as disobedience. Peter Finch as the surgeon she works under in Africa is especially useful. Because while the film never breaches any real romantic element between the two, he is still clear to her that her own individuality will keep her from being a successful nun. And that being a successful nun will keep her from being an effective medical practitioner.
The direction is effective but never quite as stark throughout the entire 2:30 as it is in its initial church locations, as well as the film's final scene. Also, I didn't see the need for the full run time. An extended illness may have been factual, but wasn't required. In the end, the film is not overtly inspirational- nor is it at all cynical. It's a very real portrayal of the line between right and righteous.