understands that Amir has been living with the guilt of his decision for decades. When Rahim Khan calls Amir from Pakistan and informs him of his present physical condition, he is confident that Amir will visit him. Rahim Khan also knows that Hassan is Amir's half-brother, which is something that Amir does not know. Rahim's plan is to tell Amir the truth about Hassan being his half-brother, then inform him of Sohrab's present circumstance in hopes that Amir will travel into Taliban-occupied Kabul to save Hassan's son. Fortunately, Amir ends up atoning for his past sins by saving Sohrab, adopting him, and bringing him to America. 

One of the main themes of this novel is redemption.  When Amir and his father fled Kabul and went to the United States there was a shadow of shame over Amir.  In "The Kite Runner" Amir had shamed himself by not coming forward and helping Hassan when he was attacked. Amir shamed himself even further by lying when asked if he knew what was wrong with Hassan and further, he created a situation in which Hassan was accused of stealing and had to leave his home. Amir was so determined to win his father's love for himself and only himself that he hurt Hassan in the process.  His years from that point on were filled with guilt. He needed redemption.

When Rahim called Amir and told Amir that he needed to come back home Amir was unsure.  Rahim told him that he needed to come to right the wrongs that had been done, that "there is a way to be good again" indicated to Amir that there was an action he could take to redeem himself from the wrongs he had committed in his youth.

The reader later learns that Hassan was his half brother and that he had had a son.  Amir could make things good again by saving his nephew.

In The Kite Runner (Hosseini), one of the most powerful themes of the story is set forth in the simple statement of Rahim Khan, the old family friend of Baba and Amir, "There is a way to be good again" (2).  Amir must live with the guilt of his sins against Hassan, amongst these a failure to rescue his friend from being bullied and raped by Assef and his despicable act of framing Hassan for theft.  He has no opportunity for redemption, even supposing he had been capable of it.  He and Baba are forced to flee Afghanistan, and Ali and Hassan, who have left Baba's house, are left behind to face the chaos that Afghanistan has become.  Amir, in his dealings with Hassan, has not been good.

What Khan is offering is a chance at redemption.  That is the overarching theme of the novel. In order to be redeemed from one's sins, at the most basic level one must atone and be good again, trying to make up for what one has done.  Amir cannot bring back Ali and Hassan, who have died.  Nor can he make up for all of the sorrows they must have endured, but he can face down the enemy he so cowardly ran from, Assef, and he can rescue Sohrab, Ali's son and, as he learns, his nephew, from the clutches of the Taliban.  The reader knows nothing of this at the beginning, but the more we read of the story, the more we come to understand Khan's wisdom in offering this chance to Amir.

Khan plays a very quiet role in the story, but he is best positioned to understand Amir and how damaged Amir's life has been, by forces beyond his own control and by his own behavior.  Khan is the one who knows that Hassan is the child of Baba.  Khan is the one who sees how easily Amir lords it over Hassan because Amir is from a wealthy Sunni Pashtun family while Hassan is a mere servant who is a Shi'a Hazara, part of an ill-treated minority.  Khan is the one who knows that love is not meant to stop at an ethnic or religious line because he himself loved a Hazara woman.  Khan understands that Amir has good in him, but fears that he will never be whole without some form of redemption.  To be good again implies that there was a time when Amir had been a good person, and Khan believes he can be one again.