Wealthier, more corrupt "master" is a recurring motif in The Kite Runner, and Amir and Baba's feelings of guilt for their betrayals drive much of the novel's action. The central betrayal comes when Amir watches and does nothing as Hassan, who has always stood up for Amir in the past, gets raped by Assef. Amir then worsens the betrayal by driving Ali and Hassan from the household. Later in the book, Amir learns that Baba also betrayed his own best friend and servant - Ali, Hassan's father - by fathering a child (Hassan) with Ali's wife Sanaubar. This knowledge comes as another kind of betrayal for Amir, who had always hero-worshipped Baba and is shocked to learn of his father's flaws.