Five days later, Christopher sees five red cars in a row on his way to school, making the day a Super Good Day. He feels that something special will happen. When he gets home, he goes to the shop at the end of the road to buy candy and runs into Mrs. Alexander from house number thirty-nine. Mrs. Alexander asks where he went the other day. When she brought out the biscuits for him, he was gone. Christopher confesses he was afraid she would call the police because he was poking his nose into other people’s business.
Christopher exits the shop and pets Mrs. Alexander’s dog, which is tied up. He realizes Father didn’t ban him from talking about Mr. Shears outside of the house, so he asks Mrs. Alexander about Mr. Shears. She remarks that Christopher knows why Father doesn’t like Mr. Shears much. When Christopher asks if Mr. Shears killed Mother, Mrs. Alexander expresses shock to learn that Mother is dead and assures Christopher that Mr. Shears didn’t kill Mother.
Christopher asks Mrs. Alexander why she said he knew why Father didn’t like Mr. Shears. Mrs. Alexander reveals that Mr. Shears and Mother had an affair. She explains that Father dislikes Mr. Shears as a result, and that Christopher should not mention Mr. Shears in front of Father. Mrs. Alexander makes Christopher promise not to tell Father about their conversation. Christopher goes home.
Christopher tells us that Mr. Jeavons believes Christopher likes math because, in math, straightforward answers exist for every problem, unlike in life. Christopher disagrees that math problems always have straightforward answers, and uses the Monty Hall problem as proof. In 1990, a reader sent a question to Marilyn vos Savant, a columnist at Parade magazine, who had the world’s highest IQ. The question asked what to do on a game show in which you try to win a car by picking one of three doors. Two of the doors hide goats, while one hides a car. When you pick a door, the host opens one of the two other doors to show a goat, then gives you a chance to change doors. In her answer, vos Savant said you should always change the door you have picked. After she published her answer, mathematicians and scientists wrote in claiming she was wrong, but in fact the math backs up vos Savant’s advice. Christopher thinks the problem shows that intuition can be wrong, and that sometimes numbers are complicated and not straightforward at all.
Christopher’s search for information about Wellington’s murderer inadvertently turns up information about his own family. In fact, Chapter 97 marks a pivotal moment in the narrative, as Mrs. Alexander reveals to Christopher that Mr. Shears and Christopher’s mother had an affair. The revelation puts into perspective Father’s angry outburst in the previous section, and perhaps the earlier incident when Christopher found his father crying after they came back from the police station as well. Christopher’s father evidently knew about the affair between Christopher’s mother and Mr. Shears, and he still feels angry toward Mr. Shears as a result. Christopher, on the other hand, apparently had no idea. When Mrs. Alexander tells him, he seems shocked and just wants to go home rather than continuing with his investigation. Christopher set out to uncover the person who committed one crime, but instead discovered the truth about his parents and his father’s reason for disliking Mr. Shears.
Although Christopher doesn’t give much description of his emotional response to this news, he gives some hints about his feelings through his explanation of the Monty Hall problem. In essence, Christopher shows that intuition, which says is what people use in life to make decisions, can lead a person to the wrong answer. A problem that appears straightforward turns out to be not straightforward at all. Christopher never explicitly connects the Monty Hall problem to Mrs. Alexander’s revelation about his mother. But the fact that this seeming digression follows immediately after Christopher’s conversation with Mrs. Alexander suggests that Christopher sees a parallel between the two. In other words, Christopher feels his own intuition about Mother was wrong, leaving him confused and uncomfortable.