Sara didn’t like Joe at first because she thinks he took Charlie’s watch.
Charlie is Sara’s mentally-challenged brother. She is fiercely protective of him. The watch is very important to Charlie, because its ticking comforts him when he is upset.
“You believe what you want then, but I didn’t take that watch. I thought the matter had been settled.” (ch 14, p. 79)
After she refuses to talk to him for several months, Charlie is finally able to convince Sara that he is not a bad person. When Sara can’t find Charlie, she and Mary decide to look for him. They find Joe, who insists again that he did not take the watch. They let him look for Charlie with them.
Mary tells Sara that she knows Joe did not steal Charlie’s watch. In fact, he was able to give it back to Charlie after getting it from the boys who did steal it. After Sara realizes this, she apologizes and she and Joe can become friends. Joe seems to like Charlie, and even helps Sara with him. Sara rewards him by going to a party with him. Sara realized that you should not judge people until you have the whole story, because people are not always what they seem.