Part three of "Only the Heart" is about the highs and lows of the Vo family and looks at the idea of "Yin and Yang".
The grandmother, Vo Kim Tuyet is depicted in part three as a spiritual person who believes strongly in"Yin and Yang". She makes predictions about the events which unfold later in the story. She predicts that "evil" or bad things will happen in order to restore the balance of Yin and Yang.
Since coming to Australia the Vo family has been very fortunate. As well as getting away from their communist county to a free one, Toan experiences success in school and later on as an actor. Vo Kin Tueyt believes that in order to restore the balance of good and evil something bad will happen, "good and evil, light and dark".
Near the end of the novel something bad does happen, Linh and Miro are involved in a car accident while being chased by gang member.
They end up in hospital and it is found that Linh has lost the use of her legs. This is a good example of the evil side of the grandmother's predictions.
In the accident Linh loses movement in her legs for the rest of her life. This is a sign that evil has set upon her for her entire life and no amount of good can restore the balance and reverse the damage done.
Not even when Linh gets revenge by seeing Tang killed.
On the other hand, Toan experiences the opposite. Everything that happens to Toan is for the better. He does well at school and later becomes a successful TV actor.