This is the background of the story. This event occurs before the beginning of the story. This is the reason why we find George and Lennie walking along the road in the beginning of the story. Lennie tries to touch a girls dress but the girl freaks out when he does. This causes him to tighten his grip which rips her dress. She the calls the police and claims that she was raped, meanwhile George has grabbed Lennie and are running away. Then that leads to when we first see them in the story.