Enrico Melotti, a middle-aged businessman, is dominated by a fierce as naive form of machismo and sees women only for what they can give him, both in terms of emotional and sexual satisfaction, and in terms of labor services and domestic labor. Therefore, he has a difficult relationship with his wife Marisa, his secretary/lover Claudia and his maid Teresa.

During a business trip to America, his friend Arturo shows him how he solved the same problems. At Arturo's home, Enrico is astonished in seeing Caterina, a female-looking robotic maid that does all domestic chores better than a human because it doesn't need to sleep or feed. The only thing that puzzles Enrico is that the robot keeps calling Arturo by phone at regular intervals, as if to show concern like a human mate.

Returning home from the trip, Enrico has again arguments with Claudia, Teresa and Marisa: he ignores Claudia's complaints (she would have him leave his wife and be with her in the public), he disapproves of Marisa having a job and a social life, and demands that Teresa perform extra activities on her evening off.

Enrico resolves to break the relationship with the three women and to buy a Caterina robot for domestic duties, determined to live alone and not having to answer to anyone. At first, although spending is significant, everything seems to be going well, although Catherine shows strange (almost human) reactions and gives some strange sign of unrest during a visit from Marisa.

Enrico believes that he has solved all of his problems, and starts looking for a female companion that does not demand so much as his former ones. He invites home the young and beautiful Elisabetta, whom he met at Marisa's store. The girl becomes uneasy at the sight of Caterina (as Enrico's ex-wife had been), especially after the robot seems to reject her as it did with Marisa.

When Enrico and Elisabetta are about to spend the night together, Caterina loses control, plays havoc with the house and even tries to kill its master. Elisabetta panics, runs away and disappears from Enrico's life.

The intervention of the engineer who built the robot is of little help: Caterina, in fact, is such a sophisticated machine that it acquired almost total autonomy from its original setting. In front of the engineer it pretends to behave, in order not to be removed and replaced, but as soon as the technician goes away, she starts imposing conditions on Enrico: she will serve him devoutly and without complaining if he will give her the respect and dedication owed to a real woman.

So, when an American girl phones Enrico asking to be hosted at his home, the man vehemently answers no, in fear of a possible retaliation from the robot. The film ends with Enrico having dinner alone, duly served by Caterina in a room where she has closed all the doors like in a jail.