After winning a poker game without realizing, Homer is called slow by his friends. Wishing to prove them wrong, he decides to sign up for an adult education class. Not finding anything, he becomes a teacher himself, running a course on how to build a successful marriage.
However, he does not know anything about teaching, and his class is unsuccessful until he starts spilling personal secrets about his love life. Marge dislikes this and tells Homer not to say anything more about their personal life. But when it happens again, Marge kicks Homer out of the house, and he ends up living in the treehouse.
Marge will not take Homer back, telling him that he has betrayed her trust. Homer tells her how much he loves her and that he cannot afford to lose her trust again. Marge forgives him.