In Irrational Man, Abe Lucas is a professor of philosophy who is going through an enormous existential crisis. He does not see sense in his life and tries to make some changes, going to teach a very small university.
There she meets Rita Richards, a teacher who is not very happy with her marriage. That is why he approaches Abe, in order to start a relationship with him that rescues her from his marriage, but Abe does not want to know anything about her.
Another person he meets in his new destination is Jill Pollard. She is their best student and that makes them become friends. She has a boyfriend, of whom she is in love, but the truth is that her teacher attracts her a lot.
That makes the two come too close, too, because Abe falls in love with her. Jill feels a deep fascination for her teacher, so much so that it does not decrease even though Abe shows that she has serious mental problems.