The disturbing rape scene in this excellent novel occurs in Chapter Seven. They begin as Assef charges at Hassan and overpowers him. As Amir bites on his fist and shuts his eyes, he has three memories. Firstly, he remembers someone telling him how he and Hassan actually fed from the same breast, which, according to the anonymous narrator, creates a "brotherhood." This of course highlights the true betrayal in Amir's inaction to stand up for his friend (who is actually his brother, and not just in a metaphorical sense.)
Secondly, he remembers when he and Hassan went to a fortune teller, and as the fortune teller feels Hassan's palm and face, a "shadow passes across the old man's face" and he returns the money to Hassan, obviously indicating that he predicts something bad will happen to Hassan. The sadness in Hassan's future only begins with the rape of course, as we go on to discover as we read the novel.
Lastly, Amir has a kind of dream when the hand of Hassan, gashed and bleeding, pulls him up and saves him from asnowstorm. As they hold hands, the scene is replaced with one of beauty and they look up to see a sky full of kites. This could foreshadow the final ending of the novel, which is when Amir is finally able to emotionally connect with Sohrab, Hassan's son.