The theme of secrets and truth versus lies becomes dominant once Amir learns that Hassan was his half-brother. Rahim Khan knows this secret and he knows the secret about Hassan’s rape. His role in the novel is as the wise sage. He understands the actions and intent of Amir, Hassan and Baba and can help explain a lot of it to the adult Amir. He also understands that explaining things to the younger Amir would not have helped Amir on his journey to healing, which is why he is silent about these secrets. Amir needs to take the journey alone.

However, when Amir returns to Afghanistan many years later to get Sohrab, Rahim Khan tells him the truth. Once Amir makes the right choice and comes to Afghanistan to save Sohrab, Rahim Khan understands how far Amir has come in his journey to achieve redemption. Moreover, because Rahim Khan knows that he is dying, this is the only opportunity he has to reveal the truth about everything tell to Amir.

Baba and Ali’s relationship as boys mirrors that of Amir and Hassan’s in many ways. Both sets of boys are raised together almost as brothers. Yet, overshadowing the fraternal relationship is that fact that in each pair, there is a wide gulf between the two boys' social classes. The more privileged boy is the instigator in both relationships and the underprivileged boy takes the blame. In both relationships, the privileged boy betrays the other. Yet, as Rahim Khan understands, there is a big difference between the two betrayals. Baba knowingly betrayed Ali when the two were men and to satisfy his own desires. By comparison, Amir betrays Hassan when they are young boys because he is frightened. It is an act that plagues him for the rest of his life until he comes to rescue Sohrab, which Rahim Khan understands.