Sister Bertrille needs to see Dr. Paredes, the dentist, to have a toothache fixed, but Sister Bertrille is scared of dentists. So the Reverend Mother goes with her to hold her hand. To calm Sister Bertrille's nerves, Dr. Paredes puts her under hypnosis. However the Reverend Mother accidentally gets hypnotized at the same time. Fascinated by this, Carlos wants to see the results of the hypnosis, and as a lark, Dr. Paredes gives them a post-hypnotic suggestion: every time they hear the word "red", Sister Bertrille will act like the Reverend Mother and the Reverend Mother will act like Sister Bertrille. It works. Before Dr. Paredes needs to rush off, he fixes Sister Bertrille's tooth and brings both women out of hypnosis. However he forgets to remove the post-hypnotic suggestion. Unfortunately, this act coincides with Father Lundigan's visit to the convent, Father Lundigan the church's psychiatrist. Last Father Lundigan visited, he had a year of therapy since all the sisters tried to ...