This is the story of wife waking up one morning and realizing that she is unhappy. It is about the true meaning of marriage, but it is also about the true meaning of life. Although her husband is "there" for her physically, he is not emotionally supportive. They do not have a real connection and do not understand one another. In marriage, a partnership and a friendship should be the central focus - these two have neither.
But as she realizes this, and watches the plumber working "with" the world and not just in it, she realizes that she needs to have the same relationship with the world around her. She needs to feel that she is really a part of something, contributing and receiving. Both in her marriage and in her life as a whole. It can't all be about intellectual experience - it has to be about physical experience and interaction as well.