The young Bruno lives in an old convent with three nuns in Italy used as a guesthouse. He gives them a help, but the convent is so great as to require the collaboration of a new housekeeper, Helena. She is a young, beautiful woman and Bruno soon falls in love for her. The nuns begin to have a strange attitude, resulting not fully accepting the presence of that girl. Meanwhile, an University professor, prof. Goffredi, decides to spend a night with his two sons in that nunnery and he begins to investigate the strange origins of the convent...