A few days later, Christopher sees five red cars in a row, so he knows something special is going to happen. When he gets home from school, he goes to the corner store for candy and runs into Mrs. Alexander. He admits that on the other occasion they met, he left her yard because he thought she might call the police, but she tells him she wouldn’t have done that.
Even if Christopher may be unconsciously aware of his mental manipulation of the car rule, it still influences his actions. Perhaps he makes his own luck by going to the store rather than staying home, because he thinks the day will be special. He also exhibits his honesty again, not hesitating to tell Mrs. Alexander that he didn’t trust her.
Christopher makes friends with Mrs. Alexander’s dog outside the shop, and Mrs. Alexander tries again to chat with him. Christopher is being very careful so that he doesn’t disobey his father’s instructions to leave the neighbors alone. He tells her about what he likes, and that he’s going to take the Maths A level. Mrs. Alexander is impressed.
Mrs. Alexander again proves to be a kind and understanding influence. She respects Christopher’s mathematical abilities even while pushing him out of his comfort zone in terms of social interaction. Christopher, for his part, entirely intends to keep his promise to his father.
Christopher decides that he has to take risks as a detective, and the specific things his father made him promise to avoid don’t cover asking questions about Mr. Shears, so he asks Mrs. Alexander what she knows about him. She quickly realizes that he’s still trying to find out who killed Wellington, and tells Christopher that he probably shouldn’t be asking about such things. Mrs. Alexander thinks that Christopher already knows why his father doesn’t like Mr. Shears.
Despite Christopher’s good intentions, his curiosity wins out, and his logical mind begins to find loopholes in the promise. He convinces himself he’s not breaking it, even though Mrs. Alexander sees right through his veiled questions. Her respect for him leads her to think he has a fuller understanding of his father’s emotions than he really does. However, her reaction also implies that there is some common knowledge about his family that Christopher is missing.
Christopher begins to speculate that Mr. Shears had something to do with his mother’s death. Mrs. Alexander seems shocked. She suggests they go for a walk in the park, and although Christopher is nervous about going into the park with a stranger, he faces this fear for the sake of the mystery. Mrs. Alexander makes him promise not to tell his father she’s spoken to him, and then she carefully reveals that Christopher’s mother had an affair with Mr. Shears, and that’s why Ed hates him. Christopher leaves because he’s scared of being in the park with Mrs. Alexander.
Christopher again overcomes his social fear to successfully play his detective role. Christopher’s reaction to Mrs. Alexander’s revelation is unconventional; he doesn’t seem upset about his mother’s affair, but his anxiety about Mrs. Alexander suddenly becomes too much for him. It’s possible that his reaction to his mother’s affair simply manifests itself as an inability to continue in this socially frightening situation.