Christopher Durang must have been taught by a memorably awful nun, because he just can't let go of the concept. The play, "Sister Mary Ignatius Explains It All For You," was presented -- at least in Hollywood -- in precisely the same tone as Diane Keaton's lecture scenes here. Sister Mary was an exaggeration, a lampoon, a bitter satire of a serenely confident, doctrinaire and highly judgmental nun -- and as played by Lynn Redgrave, she was hilarious. But the movie insists that we take this exaggeration absolutely seriously -- while, as mentioned, maintaining the same tone in the "explains it all" scenes. The two approaches clash headlong and in the last twenty minutes, the movie goes off the track, plunges into the gorge, and explodes. There are no survivors. It could have worked, if the tone of the scenes with the four former students, and their encounter with Sister Mary, been pitched the same as the Sister Mary scenes. Or if the Sister Mary scenes been presented more realistically. This way simply doesn't work at all.