Hosseini constructs the kite-flying episode in Chapter 7 to further develop the relationship between Amir and Hassan. Though Amir is nervous, Hassan continually encourages him, and the competition ultimately ends with Amir's victory. When Hassan takes the blue kite to run it for Amir in celebration, Amir's focus shifts to his thoughts of Baba, whom he has finally made proud.
During this time, Amir loses track of Hassan, and the scene that follows--in which Hassan is raped by Assef--is one of the most poignant and disturbing in the novel. For, Amir, a witness to this horrible act, is unable to act in Hassan's defense. Afterwards, Hassan returns home, traumatized both physically and emotionally, holding the blue kite. For the rest of the novel, Amir's guilt, coupled with Hassan's presence and failure to ever mention the situation again, proves to be too much for Amir; he ultimately constructs and executes a plan to drive Ali and Hassan from Baba's home. This episode serves as a reminder to Amir, and to readers, of Hassan's unrivaled love for and commitment to Amir; Amir's failure to reciprocate is an issue with which he is left to deal with for the rest of his life.
In Chapter 25, the final chapter in the novel, an adult Amir buys Sohrab a kite and takes him out to run it. After a tumultuous year in which Sohrab refused to speak and even tried to commit suicide to avoid being placed in an orphanage, this kite-running experience evokes Sohrab's first smile in Amir's presence. As Sohrab is Hassan's son, and as Amir has gone through many extraordinarily difficult and trying situations with the child, this smile is what Amir refers to as a "small, wondrous thing." The novel closes with Sohrab and Amir running kites together with the hope that both will move forward together from the difficulties that each has endured.